diff --git a/p2p/base/dtlstransportchannel_unittest.cc b/p2p/base/dtlstransportchannel_unittest.cc
index 95696e2..e62563e 100644
--- a/p2p/base/dtlstransportchannel_unittest.cc
+++ b/p2p/base/dtlstransportchannel_unittest.cc
@@ -75,8 +75,6 @@
     transport_->SetIceRole(role);
     transport_->SetIceTiebreaker(
         (role == cricket::ICEROLE_CONTROLLING) ? 1 : 2);
-    transport_->SignalWritableState.connect(this,
-        &DtlsTestClient::OnTransportWritableState);
 
     for (int i = 0; i < count; ++i) {
       cricket::DtlsTransportChannelWrapper* channel =
@@ -193,7 +191,15 @@
   }
 
   bool all_channels_writable() const {
-    return transport_->all_channels_writable();
+    if (channels_.empty()) {
+      return false;
+    }
+    for (cricket::DtlsTransportChannelWrapper* channel : channels_) {
+      if (!channel->writable()) {
+        return false;
+      }
+    }
+    return true;
   }
 
   void CheckRole(rtc::SSLRole role) {
@@ -313,11 +319,6 @@
     return (num_matches < ((static_cast<int>(size) - 5) / 10));
   }
 
-  // Transport callbacks
-  void OnTransportWritableState(cricket::Transport* transport) {
-    LOG(LS_INFO) << name_ << ": is writable";
-  }
-
   // Transport channel callbacks
   void OnTransportChannelWritableState(cricket::TransportChannel* channel) {
     LOG(LS_INFO) << name_ << ": Channel '" << channel->component()
diff --git a/p2p/base/transport.cc b/p2p/base/transport.cc
index 3e5f1b9..66ba63e 100644
--- a/p2p/base/transport.cc
+++ b/p2p/base/transport.cc
@@ -17,7 +17,7 @@
 #include "webrtc/p2p/base/port.h"
 #include "webrtc/p2p/base/transportchannelimpl.h"
 #include "webrtc/base/bind.h"
-#include "webrtc/base/common.h"
+#include "webrtc/base/checks.h"
 #include "webrtc/base/logging.h"
 
 namespace cricket {
@@ -69,59 +69,22 @@
     : name_(name), allocator_(allocator) {}
 
 Transport::~Transport() {
-  ASSERT(channels_destroyed_);
-}
-
-bool Transport::AllChannelsCompleted() const {
-  // We aren't completed until at least one channel is complete, so if there
-  // are no channels, we aren't complete yet.
-  if (channels_.empty()) {
-    LOG(LS_INFO) << name() << " transport is not complete"
-                 << " because it has no TransportChannels";
-    return false;
-  }
-
-  // A Transport's ICE process is completed if all of its channels are writable,
-  // have finished allocating candidates, and have pruned all but one of their
-  // connections.
-  for (const auto& iter : channels_) {
-    const TransportChannelImpl* channel = iter.second.get();
-    bool complete =
-        channel->writable() &&
-        channel->GetState() == TransportChannelState::STATE_COMPLETED &&
-        channel->GetIceRole() == ICEROLE_CONTROLLING &&
-        channel->gathering_state() == kIceGatheringComplete;
-    if (!complete) {
-      LOG(LS_INFO) << name() << " transport is not complete"
-                   << " because a channel is still incomplete.";
-      return false;
-    }
-  }
-
-  return true;
-}
-
-bool Transport::AnyChannelFailed() const {
-  for (const auto& iter : channels_) {
-    if (iter.second->GetState() == TransportChannelState::STATE_FAILED) {
-      return true;
-    }
-  }
-  return false;
+  RTC_DCHECK(channels_destroyed_);
 }
 
 void Transport::SetIceRole(IceRole role) {
   ice_role_ = role;
-  for (auto& iter : channels_) {
-    iter.second->SetIceRole(ice_role_);
+  for (const auto& kv : channels_) {
+    kv.second->SetIceRole(ice_role_);
   }
 }
 
 bool Transport::GetRemoteSSLCertificate(rtc::SSLCertificate** cert) {
-  if (channels_.empty())
+  if (channels_.empty()) {
     return false;
+  }
 
-  ChannelMap::iterator iter = channels_.begin();
+  auto iter = channels_.begin();
   return iter->second->GetRemoteSSLCertificate(cert);
 }
 
@@ -155,8 +118,8 @@
 
   local_description_.reset(new TransportDescription(description));
 
-  for (auto& iter : channels_) {
-    ret &= ApplyLocalTransportDescription(iter.second.get(), error_desc);
+  for (const auto& kv : channels_) {
+    ret &= ApplyLocalTransportDescription(kv.second, error_desc);
   }
   if (!ret) {
     return false;
@@ -186,8 +149,8 @@
   }
 
   remote_description_.reset(new TransportDescription(description));
-  for (auto& iter : channels_) {
-    ret &= ApplyRemoteTransportDescription(iter.second.get(), error_desc);
+  for (const auto& kv : channels_) {
+    ret &= ApplyRemoteTransportDescription(kv.second, error_desc);
   }
 
   // If PRANSWER/ANSWER is set, we should decide transport protocol type.
@@ -202,67 +165,48 @@
 }
 
 TransportChannelImpl* Transport::CreateChannel(int component) {
-  TransportChannelImpl* impl;
+  TransportChannelImpl* channel;
 
   // Create the entry if it does not exist.
-  bool impl_exists = false;
-  auto iterator = channels_.find(component);
-  if (iterator == channels_.end()) {
-    impl = CreateTransportChannel(component);
-    iterator = channels_.insert(std::pair<int, ChannelMapEntry>(
-        component, ChannelMapEntry(impl))).first;
+  bool channel_exists = false;
+  auto iter = channels_.find(component);
+  if (iter == channels_.end()) {
+    channel = CreateTransportChannel(component);
+    channels_.insert(std::pair<int, TransportChannelImpl*>(component, channel));
   } else {
-    impl = iterator->second.get();
-    impl_exists = true;
+    channel = iter->second;
+    channel_exists = true;
   }
 
-  // Increase the ref count.
-  iterator->second.AddRef();
   channels_destroyed_ = false;
 
-  if (impl_exists) {
-    // If this is an existing channel, we should just return it without
-    // connecting to all the signal again.
-    return impl;
+  if (channel_exists) {
+    // If this is an existing channel, we should just return it.
+    return channel;
   }
 
   // Push down our transport state to the new channel.
-  impl->SetIceRole(ice_role_);
-  impl->SetIceTiebreaker(tiebreaker_);
-  impl->SetIceConfig(ice_config_);
+  channel->SetIceRole(ice_role_);
+  channel->SetIceTiebreaker(tiebreaker_);
+  channel->SetIceConfig(ice_config_);
   // TODO(ronghuawu): Change CreateChannel to be able to return error since
   // below Apply**Description calls can fail.
   if (local_description_)
-    ApplyLocalTransportDescription(impl, NULL);
+    ApplyLocalTransportDescription(channel, nullptr);
   if (remote_description_)
-    ApplyRemoteTransportDescription(impl, NULL);
+    ApplyRemoteTransportDescription(channel, nullptr);
   if (local_description_ && remote_description_)
-    ApplyNegotiatedTransportDescription(impl, NULL);
-
-  impl->SignalWritableState.connect(this, &Transport::OnChannelWritableState);
-  impl->SignalReceivingState.connect(this, &Transport::OnChannelReceivingState);
-  impl->SignalGatheringState.connect(this, &Transport::OnChannelGatheringState);
-  impl->SignalCandidateGathered.connect(this,
-                                        &Transport::OnChannelCandidateGathered);
-  impl->SignalRouteChange.connect(this, &Transport::OnChannelRouteChange);
-  impl->SignalRoleConflict.connect(this, &Transport::OnRoleConflict);
-  impl->SignalConnectionRemoved.connect(
-      this, &Transport::OnChannelConnectionRemoved);
+    ApplyNegotiatedTransportDescription(channel, nullptr);
 
   if (connect_requested_) {
-    impl->Connect();
-    if (channels_.size() == 1) {
-      // If this is the first channel, then indicate that we have started
-      // connecting.
-      SignalConnecting(this);
-    }
+    channel->Connect();
   }
-  return impl;
+  return channel;
 }
 
 TransportChannelImpl* Transport::GetChannel(int component) {
-  ChannelMap::iterator iter = channels_.find(component);
-  return (iter != channels_.end()) ? iter->second.get() : NULL;
+  auto iter = channels_.find(component);
+  return (iter != channels_.end()) ? iter->second : nullptr;
 }
 
 bool Transport::HasChannels() {
@@ -270,32 +214,13 @@
 }
 
 void Transport::DestroyChannel(int component) {
-  ChannelMap::iterator iter = channels_.find(component);
+  auto iter = channels_.find(component);
   if (iter == channels_.end())
     return;
 
-  TransportChannelImpl* impl = NULL;
-
-  iter->second.DecRef();
-  if (!iter->second.ref()) {
-    impl = iter->second.get();
-    channels_.erase(iter);
-  }
-
-  if (connect_requested_ && channels_.empty()) {
-    // We're no longer attempting to connect.
-    SignalConnecting(this);
-  }
-
-  if (impl) {
-    DestroyTransportChannel(impl);
-    // Need to update aggregate state after destroying a channel,
-    // for example if it was the only one that wasn't yet writable.
-    UpdateWritableState();
-    UpdateReceivingState();
-    UpdateGatheringState();
-    MaybeSignalCompleted();
-  }
+  TransportChannelImpl* channel = iter->second;
+  channels_.erase(iter);
+  DestroyTransportChannel(channel);
 }
 
 void Transport::ConnectChannels() {
@@ -316,14 +241,11 @@
     TransportDescription desc(
         std::vector<std::string>(), rtc::CreateRandomString(ICE_UFRAG_LENGTH),
         rtc::CreateRandomString(ICE_PWD_LENGTH), ICEMODE_FULL,
-        CONNECTIONROLE_NONE, NULL, Candidates());
-    SetLocalTransportDescription(desc, CA_OFFER, NULL);
+        CONNECTIONROLE_NONE, nullptr, Candidates());
+    SetLocalTransportDescription(desc, CA_OFFER, nullptr);
   }
 
   CallChannels(&TransportChannelImpl::Connect);
-  if (HasChannels()) {
-    SignalConnecting(this);
-  }
 }
 
 void Transport::MaybeStartGathering() {
@@ -333,24 +255,16 @@
 }
 
 void Transport::DestroyAllChannels() {
-  std::vector<TransportChannelImpl*> impls;
-  for (auto& iter : channels_) {
-    iter.second.DecRef();
-    if (!iter.second.ref())
-      impls.push_back(iter.second.get());
+  for (const auto& kv : channels_) {
+    DestroyTransportChannel(kv.second);
   }
-
   channels_.clear();
-
-  for (TransportChannelImpl* impl : impls) {
-    DestroyTransportChannel(impl);
-  }
   channels_destroyed_ = true;
 }
 
 void Transport::CallChannels(TransportChannelFunc func) {
-  for (const auto& iter : channels_) {
-    ((iter.second.get())->*func)();
+  for (const auto& kv : channels_) {
+    (kv.second->*func)();
   }
 }
 
@@ -389,13 +303,13 @@
 bool Transport::GetStats(TransportStats* stats) {
   stats->transport_name = name();
   stats->channel_stats.clear();
-  for (auto iter : channels_) {
-    ChannelMapEntry& entry = iter.second;
+  for (auto kv : channels_) {
+    TransportChannelImpl* channel = kv.second;
     TransportChannelStats substats;
-    substats.component = entry->component();
-    entry->GetSrtpCipher(&substats.srtp_cipher);
-    entry->GetSslCipher(&substats.ssl_cipher);
-    if (!entry->GetStats(&substats.connection_infos)) {
+    substats.component = channel->component();
+    channel->GetSrtpCipher(&substats.srtp_cipher);
+    channel->GetSslCipher(&substats.ssl_cipher);
+    if (!channel->GetStats(&substats.connection_infos)) {
       return false;
     }
     stats->channel_stats.push_back(substats);
@@ -418,170 +332,15 @@
     }
   }
 
-  for (std::vector<Candidate>::const_iterator iter = candidates.begin();
-       iter != candidates.end();
-       ++iter) {
-    TransportChannelImpl* channel = GetChannel(iter->component());
-    if (channel != NULL) {
-      channel->AddRemoteCandidate(*iter);
+  for (const Candidate& candidate : candidates) {
+    TransportChannelImpl* channel = GetChannel(candidate.component());
+    if (channel != nullptr) {
+      channel->AddRemoteCandidate(candidate);
     }
   }
   return true;
 }
 
-void Transport::OnChannelWritableState(TransportChannel* channel) {
-  LOG(LS_INFO) << name() << " TransportChannel " << channel->component()
-               << " writability changed to " << channel->writable()
-               << ". Check if transport is complete.";
-  UpdateWritableState();
-  MaybeSignalCompleted();
-}
-
-void Transport::OnChannelReceivingState(TransportChannel* channel) {
-  UpdateReceivingState();
-}
-
-TransportState Transport::GetTransportState(TransportStateType state_type) {
-  bool any = false;
-  bool all = !channels_.empty();
-  for (const auto iter : channels_) {
-    bool b = false;
-    switch (state_type) {
-      case TRANSPORT_WRITABLE_STATE:
-        b = iter.second->writable();
-        break;
-      case TRANSPORT_RECEIVING_STATE:
-        b = iter.second->receiving();
-        break;
-      default:
-        ASSERT(false);
-    }
-    any |= b;
-    all &=  b;
-  }
-
-  if (all) {
-    return TRANSPORT_STATE_ALL;
-  } else if (any) {
-    return TRANSPORT_STATE_SOME;
-  }
-
-  return TRANSPORT_STATE_NONE;
-}
-
-void Transport::OnChannelGatheringState(TransportChannelImpl* channel) {
-  ASSERT(channels_.find(channel->component()) != channels_.end());
-  UpdateGatheringState();
-  if (gathering_state_ == kIceGatheringComplete) {
-    // If UpdateGatheringState brought us to kIceGatheringComplete, check if
-    // our connection state is also "Completed". Otherwise, there's no point in
-    // checking (since it would only produce log messages).
-    MaybeSignalCompleted();
-  }
-}
-
-void Transport::OnChannelCandidateGathered(TransportChannelImpl* channel,
-                                           const Candidate& candidate) {
-  // We should never signal peer-reflexive candidates.
-  if (candidate.type() == PRFLX_PORT_TYPE) {
-    ASSERT(false);
-    return;
-  }
-
-  ASSERT(connect_requested_);
-  std::vector<Candidate> candidates;
-  candidates.push_back(candidate);
-  SignalCandidatesGathered(this, candidates);
-}
-
-void Transport::OnChannelRouteChange(TransportChannel* channel,
-                                     const Candidate& remote_candidate) {
-  SignalRouteChange(this, remote_candidate.component(), remote_candidate);
-}
-
-void Transport::OnRoleConflict(TransportChannelImpl* channel) {
-  SignalRoleConflict();
-}
-
-void Transport::OnChannelConnectionRemoved(TransportChannelImpl* channel) {
-  LOG(LS_INFO) << name() << " TransportChannel " << channel->component()
-               << " connection removed. Check if transport is complete.";
-  MaybeSignalCompleted();
-
-  // Check if the state is now Failed.
-  // Failed is only available in the Controlling ICE role.
-  if (channel->GetIceRole() != ICEROLE_CONTROLLING) {
-    return;
-  }
-
-  // Failed can only occur after candidate gathering has stopped.
-  if (channel->gathering_state() != kIceGatheringComplete) {
-    return;
-  }
-
-  if (channel->GetState() == TransportChannelState::STATE_FAILED) {
-    // A Transport has failed if any of its channels have no remaining
-    // connections.
-    SignalFailed(this);
-  }
-}
-
-void Transport::MaybeSignalCompleted() {
-  if (AllChannelsCompleted()) {
-    LOG(LS_INFO) << name() << " transport is complete"
-                 << " because all the channels are complete.";
-    SignalCompleted(this);
-  }
-  // TODO(deadbeef): Should we do anything if we previously were completed,
-  // but now are not (if, for example, a new remote candidate is added)?
-}
-
-void Transport::UpdateGatheringState() {
-  IceGatheringState new_state = kIceGatheringNew;
-  bool any_gathering = false;
-  bool all_complete = !channels_.empty();
-  for (const auto& kv : channels_) {
-    any_gathering =
-        any_gathering || kv.second->gathering_state() != kIceGatheringNew;
-    all_complete =
-        all_complete && kv.second->gathering_state() == kIceGatheringComplete;
-  }
-  if (all_complete) {
-    new_state = kIceGatheringComplete;
-  } else if (any_gathering) {
-    new_state = kIceGatheringGathering;
-  }
-
-  if (gathering_state_ != new_state) {
-    gathering_state_ = new_state;
-    if (gathering_state_ == kIceGatheringGathering) {
-      LOG(LS_INFO) << "Transport: " << name_ << ", gathering candidates";
-    } else if (gathering_state_ == kIceGatheringComplete) {
-      LOG(LS_INFO) << "Transport " << name() << " gathering complete.";
-    }
-    SignalGatheringState(this);
-  }
-}
-
-void Transport::UpdateReceivingState() {
-  TransportState receiving = GetTransportState(TRANSPORT_RECEIVING_STATE);
-  if (receiving_ != receiving) {
-    receiving_ = receiving;
-    SignalReceivingState(this);
-  }
-}
-
-void Transport::UpdateWritableState() {
-  TransportState writable = GetTransportState(TRANSPORT_WRITABLE_STATE);
-  LOG(LS_INFO) << name() << " transport writable state changed? " << writable_
-               << " => " << writable;
-  if (writable_ != writable) {
-    was_writable_ = (writable_ == TRANSPORT_STATE_ALL);
-    writable_ = writable;
-    SignalWritableState(this);
-  }
-}
-
 bool Transport::ApplyLocalTransportDescription(TransportChannelImpl* ch,
                                                std::string* error_desc) {
   ch->SetIceCredentials(local_description_->ice_ufrag,
@@ -623,9 +382,10 @@
   // between future SetRemote/SetLocal invocations and new channel
   // creation, we have the negotiation state saved until a new
   // negotiation happens.
-  for (auto& iter : channels_) {
-    if (!ApplyNegotiatedTransportDescription(iter.second.get(), error_desc))
+  for (const auto& kv : channels_) {
+    if (!ApplyNegotiatedTransportDescription(kv.second, error_desc)) {
       return false;
+    }
   }
   return true;
 }
diff --git a/p2p/base/transport.h b/p2p/base/transport.h
index 10b289c..a3daa39 100644
--- a/p2p/base/transport.h
+++ b/p2p/base/transport.h
@@ -65,21 +65,6 @@
   kIceGatheringComplete,
 };
 
-// For "writable" and "receiving", we need to differentiate between
-// none, all, and some.
-enum TransportState {
-  TRANSPORT_STATE_NONE = 0,
-  TRANSPORT_STATE_SOME,
-  TRANSPORT_STATE_ALL
-};
-
-// When checking transport state, we need to differentiate between
-// "writable" or "receiving" check.
-enum TransportStateType {
-  TRANSPORT_WRITABLE_STATE = 0,
-  TRANSPORT_RECEIVING_STATE
-};
-
 // Stats that we can return about the connections for a transport channel.
 // TODO(hta): Rename to ConnectionStats
 struct ConnectionInfo {
@@ -165,37 +150,10 @@
   // Returns the port allocator object for this transport.
   PortAllocator* port_allocator() { return allocator_; }
 
-  // Returns the states of this manager.  These bits are the ORs
-  // of the corresponding bits on the managed channels.  Each time one of these
-  // states changes, a signal is raised.
-  // TODO(honghaiz): Replace uses of writable() with any_channels_writable().
-  bool writable() const { return any_channels_writable(); }
-  bool was_writable() const { return was_writable_; }
-  bool any_channels_writable() const {
-    return (writable_ == TRANSPORT_STATE_SOME ||
-            writable_ == TRANSPORT_STATE_ALL);
-  }
-  bool all_channels_writable() const {
-    return (writable_ == TRANSPORT_STATE_ALL);
-  }
-  bool any_channel_receiving() const {
-    return (receiving_ == TRANSPORT_STATE_SOME ||
-            receiving_ == TRANSPORT_STATE_ALL);
-  }
   bool ready_for_remote_candidates() const {
     return local_description_set_ && remote_description_set_;
   }
 
-  bool AllChannelsCompleted() const;
-  bool AnyChannelFailed() const;
-
-  IceGatheringState gathering_state() const { return gathering_state_; }
-
-  sigslot::signal1<Transport*> SignalWritableState;
-  sigslot::signal1<Transport*> SignalReceivingState;
-  sigslot::signal1<Transport*> SignalCompleted;
-  sigslot::signal1<Transport*> SignalFailed;
-
   // Returns whether the client has requested the channels to connect.
   bool connect_requested() const { return connect_requested_; }
 
@@ -229,6 +187,7 @@
     return (NULL != GetChannel(component));
   }
   bool HasChannels();
+
   void DestroyChannel(int component);
 
   // Set the local TransportDescription to be used by TransportChannels.
@@ -241,10 +200,8 @@
                                      ContentAction action,
                                      std::string* error_desc);
 
-  // Tells all current and future channels to start connecting.  When the first
-  // channel begins connecting, the following signal is raised.
+  // Tells all current and future channels to start connecting.
   void ConnectChannels();
-  sigslot::signal1<Transport*> SignalConnecting;
 
   // Tells channels to start gathering candidates if necessary.
   // Should be called after ConnectChannels() has been called at least once,
@@ -260,12 +217,6 @@
 
   bool GetStats(TransportStats* stats);
 
-  sigslot::signal1<Transport*> SignalGatheringState;
-
-  // Handles sending of ready candidates and receiving of remote candidates.
-  sigslot::signal2<Transport*, const std::vector<Candidate>&>
-      SignalCandidatesGathered;
-
   // Called when one or more candidates are ready from the remote peer.
   bool AddRemoteCandidates(const std::vector<Candidate>& candidates,
                            std::string* error);
@@ -275,14 +226,6 @@
   virtual bool VerifyCandidate(const Candidate& candidate,
                                std::string* error);
 
-  // Signals when the best connection for a channel changes.
-  sigslot::signal3<Transport*,
-                   int,  // component
-                   const Candidate&> SignalRouteChange;
-
-  // Forwards the signal from TransportChannel to BaseSession.
-  sigslot::signal0<> SignalRoleConflict;
-
   virtual bool GetSslRole(rtc::SSLRole* ssl_role) const { return false; }
 
   // Must be called before channel is starting to connect.
@@ -335,74 +278,16 @@
       std::string* error_desc);
 
  private:
-  struct ChannelMapEntry {
-    ChannelMapEntry() : impl_(NULL), ref_(0) {}
-    explicit ChannelMapEntry(TransportChannelImpl *impl)
-        : impl_(impl),
-          ref_(0) {
-    }
-
-    void AddRef() { ++ref_; }
-    void DecRef() {
-      ASSERT(ref_ > 0);
-      --ref_;
-    }
-    int ref() const { return ref_; }
-
-    TransportChannelImpl* get() const { return impl_; }
-    TransportChannelImpl* operator->() const  { return impl_; }
-
-   private:
-    TransportChannelImpl* impl_;
-    int ref_;
-  };
-
-  // Candidate component => ChannelMapEntry
-  typedef std::map<int, ChannelMapEntry> ChannelMap;
-
-  // Called when the write state of a channel changes.
-  void OnChannelWritableState(TransportChannel* channel);
-
-  // Called when the receiving state of a channel changes.
-  void OnChannelReceivingState(TransportChannel* channel);
-
-  // Called when a channel starts finishes gathering candidates
-  void OnChannelGatheringState(TransportChannelImpl* channel);
-
-  // Called when a candidate is ready from channel.
-  void OnChannelCandidateGathered(TransportChannelImpl* channel,
-                                  const Candidate& candidate);
-  void OnChannelRouteChange(TransportChannel* channel,
-                            const Candidate& remote_candidate);
-  // Called when there is ICE role change.
-  void OnRoleConflict(TransportChannelImpl* channel);
-  // Called when the channel removes a connection.
-  void OnChannelConnectionRemoved(TransportChannelImpl* channel);
+  // Candidate component => TransportChannelImpl*
+  typedef std::map<int, TransportChannelImpl*> ChannelMap;
 
   // Helper function that invokes the given function on every channel.
   typedef void (TransportChannelImpl::* TransportChannelFunc)();
   void CallChannels(TransportChannelFunc func);
 
-  // Computes the AND and OR of the channel's read/write/receiving state
-  // (argument picks the operation).
-  TransportState GetTransportState(TransportStateType type);
-
-  // Sends SignalCompleted if we are now in that state.
-  void MaybeSignalCompleted();
-
-  // Sends SignalGatheringState if gathering state changed
-  void UpdateGatheringState();
-
-  void UpdateWritableState();
-  void UpdateReceivingState();
-
   const std::string name_;
   PortAllocator* const allocator_;
   bool channels_destroyed_ = false;
-  TransportState readable_ = TRANSPORT_STATE_NONE;
-  TransportState writable_ = TRANSPORT_STATE_NONE;
-  TransportState receiving_ = TRANSPORT_STATE_NONE;
-  bool was_writable_ = false;
   bool connect_requested_ = false;
   IceRole ice_role_ = ICEROLE_UNKNOWN;
   uint64 tiebreaker_ = 0;
@@ -412,7 +297,6 @@
   rtc::scoped_ptr<TransportDescription> remote_description_;
   bool local_description_set_ = false;
   bool remote_description_set_ = false;
-  IceGatheringState gathering_state_ = kIceGatheringNew;
 
   ChannelMap channels_;
 
diff --git a/p2p/base/transport_unittest.cc b/p2p/base/transport_unittest.cc
index 9febfe3..1f66a47 100644
--- a/p2p/base/transport_unittest.cc
+++ b/p2p/base/transport_unittest.cc
@@ -34,15 +34,7 @@
                       public sigslot::has_slots<> {
  public:
   TransportTest()
-      : transport_(new FakeTransport("test content name")),
-        channel_(NULL),
-        connecting_signalled_(false),
-        completed_(false),
-        failed_(false) {
-    transport_->SignalConnecting.connect(this, &TransportTest::OnConnecting);
-    transport_->SignalCompleted.connect(this, &TransportTest::OnCompleted);
-    transport_->SignalFailed.connect(this, &TransportTest::OnFailed);
-  }
+      : transport_(new FakeTransport("test content name")), channel_(NULL) {}
   ~TransportTest() {
     transport_->DestroyAllChannels();
   }
@@ -60,30 +52,10 @@
   }
 
  protected:
-  void OnConnecting(Transport* transport) {
-    connecting_signalled_ = true;
-  }
-  void OnCompleted(Transport* transport) {
-    completed_ = true;
-  }
-  void OnFailed(Transport* transport) {
-    failed_ = true;
-  }
-
   rtc::scoped_ptr<FakeTransport> transport_;
   FakeTransportChannel* channel_;
-  bool connecting_signalled_;
-  bool completed_;
-  bool failed_;
 };
 
-// Test that calling ConnectChannels triggers an OnConnecting signal.
-TEST_F(TransportTest, TestConnectChannelsDoesSignal) {
-  EXPECT_TRUE(SetupChannel());
-  transport_->ConnectChannels();
-  EXPECT_TRUE(connecting_signalled_);
-}
-
 // This test verifies channels are created with proper ICE
 // role, tiebreaker and remote ice mode and credentials after offer and
 // answer negotiations.
@@ -200,41 +172,6 @@
   EXPECT_EQ(cricket::ICEROLE_CONTROLLING, channel_->GetIceRole());
 }
 
-// This test verifies that the Completed and Failed states can be reached.
-TEST_F(TransportTest, TestChannelCompletedAndFailed) {
-  transport_->SetIceRole(cricket::ICEROLE_CONTROLLING);
-  cricket::TransportDescription local_desc(kIceUfrag1, kIcePwd1);
-  ASSERT_TRUE(transport_->SetLocalTransportDescription(local_desc,
-                                                       cricket::CA_OFFER,
-                                                       NULL));
-  EXPECT_TRUE(SetupChannel());
-
-  cricket::TransportDescription remote_desc(kIceUfrag1, kIcePwd1);
-  ASSERT_TRUE(transport_->SetRemoteTransportDescription(remote_desc,
-                                                        cricket::CA_ANSWER,
-                                                        NULL));
-
-  channel_->SetConnectionCount(2);
-  channel_->SetCandidatesGatheringComplete();
-  channel_->SetWritable(true);
-  EXPECT_TRUE_WAIT(transport_->all_channels_writable(), 100);
-  // ICE is not yet completed because there is still more than one connection.
-  EXPECT_FALSE(completed_);
-  EXPECT_FALSE(failed_);
-
-  // When the connection count drops to 1, SignalCompleted should be emitted,
-  // and completed() should be true.
-  channel_->SetConnectionCount(1);
-  EXPECT_TRUE_WAIT(completed_, 100);
-  completed_ = false;
-
-  // When the connection count drops to 0, SignalFailed should be emitted, and
-  // completed() should be false.
-  channel_->SetConnectionCount(0);
-  EXPECT_TRUE_WAIT(failed_, 100);
-  EXPECT_FALSE(completed_);
-}
-
 // Tests channel role is reversed after receiving ice-lite from remote.
 TEST_F(TransportTest, TestSetRemoteIceLiteInOffer) {
   transport_->SetIceRole(cricket::ICEROLE_CONTROLLED);
@@ -293,23 +230,3 @@
   EXPECT_EQ(1, stats.channel_stats[0].component);
 }
 
-TEST_F(TransportTest, TestReceivingStateChange) {
-  ASSERT_TRUE(SetupChannel());
-  channel_->SetConnectionCount(1);
-  transport_->ConnectChannels();
-  EXPECT_FALSE(transport_->any_channel_receiving());
-
-  channel_->SetReceiving(true);
-  EXPECT_TRUE_WAIT(transport_->any_channel_receiving(), 100);
-  FakeTransportChannel* channel2 = CreateChannel(2);
-  channel2->SetReceiving(true);
-  EXPECT_TRUE_WAIT(transport_->any_channel_receiving(), 100);
-
-  channel2->SetReceiving(false);
-  EXPECT_TRUE_WAIT(transport_->any_channel_receiving(), 100);
-
-  // After both channels become not receiving, the transport receiving state
-  // becomes TRANSPORT_STATE_NONE.
-  channel_->SetReceiving(false);
-  EXPECT_TRUE_WAIT(!transport_->any_channel_receiving(), 100);
-}
diff --git a/p2p/base/transportcontroller.cc b/p2p/base/transportcontroller.cc
index d84d574..22b827a 100644
--- a/p2p/base/transportcontroller.cc
+++ b/p2p/base/transportcontroller.cc
@@ -10,11 +10,14 @@
 
 #include "webrtc/p2p/base/transportcontroller.h"
 
+#include <algorithm>
+
 #include "webrtc/base/bind.h"
 #include "webrtc/base/checks.h"
 #include "webrtc/base/thread.h"
 #include "webrtc/p2p/base/dtlstransport.h"
 #include "webrtc/p2p/base/p2ptransport.h"
+#include "webrtc/p2p/base/port.h"
 
 namespace cricket {
 
@@ -140,8 +143,32 @@
     int component) {
   RTC_DCHECK(worker_thread_->IsCurrent());
 
+  auto it = FindChannel_w(transport_name, component);
+  if (it != channels_.end()) {
+    // Channel already exists; increment reference count and return.
+    it->AddRef();
+    return it->get();
+  }
+
+  // Need to create a new channel.
   Transport* transport = GetOrCreateTransport_w(transport_name);
-  return transport->CreateChannel(component);
+  TransportChannelImpl* channel = transport->CreateChannel(component);
+  channel->SignalWritableState.connect(
+      this, &TransportController::OnChannelWritableState_w);
+  channel->SignalReceivingState.connect(
+      this, &TransportController::OnChannelReceivingState_w);
+  channel->SignalGatheringState.connect(
+      this, &TransportController::OnChannelGatheringState_w);
+  channel->SignalCandidateGathered.connect(
+      this, &TransportController::OnChannelCandidateGathered_w);
+  channel->SignalRoleConflict.connect(
+      this, &TransportController::OnChannelRoleConflict_w);
+  channel->SignalConnectionRemoved.connect(
+      this, &TransportController::OnChannelConnectionRemoved_w);
+  channels_.insert(channels_.end(), RefCountedChannel(channel))->AddRef();
+  // Adding a channel could cause aggregate state to change.
+  UpdateAggregateStates_w();
+  return channel;
 }
 
 void TransportController::DestroyTransportChannel_w(
@@ -149,18 +176,29 @@
     int component) {
   RTC_DCHECK(worker_thread_->IsCurrent());
 
-  Transport* transport = GetTransport_w(transport_name);
-  if (!transport) {
-    ASSERT(false);
+  auto it = FindChannel_w(transport_name, component);
+  if (it == channels_.end()) {
+    LOG(LS_WARNING) << "Attempting to delete " << transport_name
+                    << " TransportChannel " << component
+                    << ", which doesn't exist.";
     return;
   }
-  transport->DestroyChannel(component);
 
+  it->DecRef();
+  if (it->ref() > 0) {
+    return;
+  }
+
+  channels_.erase(it);
+  Transport* transport = GetTransport_w(transport_name);
+  transport->DestroyChannel(component);
   // Just as we create a Transport when its first channel is created,
   // we delete it when its last channel is deleted.
   if (!transport->HasChannels()) {
     DestroyTransport_w(transport_name);
   }
+  // Removing a channel could cause aggregate state to change.
+  UpdateAggregateStates_w();
 }
 
 const rtc::scoped_refptr<rtc::RTCCertificate>&
@@ -221,6 +259,17 @@
   }
 }
 
+std::vector<TransportController::RefCountedChannel>::iterator
+TransportController::FindChannel_w(const std::string& transport_name,
+                                   int component) {
+  return std::find_if(
+      channels_.begin(), channels_.end(),
+      [transport_name, component](const RefCountedChannel& channel) {
+        return channel->transport_name() == transport_name &&
+               channel->component() == component;
+      });
+}
+
 Transport* TransportController::GetOrCreateTransport_w(
     const std::string& transport_name) {
   RTC_DCHECK(worker_thread_->IsCurrent());
@@ -240,22 +289,6 @@
   if (certificate_) {
     transport->SetLocalCertificate(certificate_);
   }
-  transport->SignalConnecting.connect(
-      this, &TransportController::OnTransportConnecting_w);
-  transport->SignalWritableState.connect(
-      this, &TransportController::OnTransportWritableState_w);
-  transport->SignalReceivingState.connect(
-      this, &TransportController::OnTransportReceivingState_w);
-  transport->SignalCompleted.connect(
-      this, &TransportController::OnTransportCompleted_w);
-  transport->SignalFailed.connect(this,
-                                  &TransportController::OnTransportFailed_w);
-  transport->SignalGatheringState.connect(
-      this, &TransportController::OnTransportGatheringState_w);
-  transport->SignalCandidatesGathered.connect(
-      this, &TransportController::OnTransportCandidatesGathered_w);
-  transport->SignalRoleConflict.connect(
-      this, &TransportController::OnTransportRoleConflict_w);
   transports_[transport_name] = transport;
 
   return transport;
@@ -270,8 +303,6 @@
     delete iter->second;
     transports_.erase(transport_name);
   }
-  // Destroying a transport may cause aggregate state to change.
-  UpdateAggregateStates_w();
 }
 
 void TransportController::DestroyAllTransports_w() {
@@ -447,49 +478,49 @@
   return transport->GetStats(stats);
 }
 
-void TransportController::OnTransportConnecting_w(Transport* transport) {
+void TransportController::OnChannelWritableState_w(TransportChannel* channel) {
+  RTC_DCHECK(worker_thread_->IsCurrent());
+  LOG(LS_INFO) << channel->transport_name() << " TransportChannel "
+               << channel->component() << " writability changed to "
+               << channel->writable() << ".";
+  UpdateAggregateStates_w();
+}
+
+void TransportController::OnChannelReceivingState_w(TransportChannel* channel) {
   RTC_DCHECK(worker_thread_->IsCurrent());
   UpdateAggregateStates_w();
 }
 
-void TransportController::OnTransportWritableState_w(Transport* transport) {
+void TransportController::OnChannelGatheringState_w(
+    TransportChannelImpl* channel) {
   RTC_DCHECK(worker_thread_->IsCurrent());
   UpdateAggregateStates_w();
 }
 
-void TransportController::OnTransportReceivingState_w(Transport* transport) {
+void TransportController::OnChannelCandidateGathered_w(
+    TransportChannelImpl* channel,
+    const Candidate& candidate) {
   RTC_DCHECK(worker_thread_->IsCurrent());
-  UpdateAggregateStates_w();
-}
 
-void TransportController::OnTransportCompleted_w(Transport* transport) {
-  RTC_DCHECK(worker_thread_->IsCurrent());
-  UpdateAggregateStates_w();
-}
-
-void TransportController::OnTransportFailed_w(Transport* transport) {
-  RTC_DCHECK(worker_thread_->IsCurrent());
-  UpdateAggregateStates_w();
-}
-
-void TransportController::OnTransportGatheringState_w(Transport* transport) {
-  RTC_DCHECK(worker_thread_->IsCurrent());
-  UpdateAggregateStates_w();
-}
-
-void TransportController::OnTransportCandidatesGathered_w(
-    Transport* transport,
-    const std::vector<Candidate>& candidates) {
-  RTC_DCHECK(worker_thread_->IsCurrent());
-  CandidatesData* data = new CandidatesData(transport->name(), candidates);
+  // We should never signal peer-reflexive candidates.
+  if (candidate.type() == PRFLX_PORT_TYPE) {
+    RTC_DCHECK(false);
+    return;
+  }
+  std::vector<Candidate> candidates;
+  candidates.push_back(candidate);
+  CandidatesData* data =
+      new CandidatesData(channel->transport_name(), candidates);
   signaling_thread_->Post(this, MSG_CANDIDATESGATHERED, data);
 }
 
-void TransportController::OnTransportRoleConflict_w() {
+void TransportController::OnChannelRoleConflict_w(
+    TransportChannelImpl* channel) {
   RTC_DCHECK(worker_thread_->IsCurrent());
 
   if (ice_role_switch_) {
-    LOG(LS_WARNING) << "Repeat of role conflict signal from Transport.";
+    LOG(LS_WARNING)
+        << "Repeat of role conflict signal from TransportChannelImpl.";
     return;
   }
 
@@ -502,6 +533,15 @@
   }
 }
 
+void TransportController::OnChannelConnectionRemoved_w(
+    TransportChannelImpl* channel) {
+  RTC_DCHECK(worker_thread_->IsCurrent());
+  LOG(LS_INFO) << channel->transport_name() << " TransportChannel "
+               << channel->component()
+               << " connection removed. Check if state is complete.";
+  UpdateAggregateStates_w();
+}
+
 void TransportController::UpdateAggregateStates_w() {
   RTC_DCHECK(worker_thread_->IsCurrent());
 
@@ -509,24 +549,24 @@
   IceGatheringState new_gathering_state = kIceGatheringNew;
   bool any_receiving = false;
   bool any_failed = false;
-  bool all_connected = HasChannels_w();
-  bool all_completed = HasChannels_w();
+  bool all_connected = !channels_.empty();
+  bool all_completed = !channels_.empty();
   bool any_gathering = false;
-  bool all_done_gathering = HasChannels_w();
-  for (const auto& kv : transports_) {
-    // Ignore transports without channels since they're about to be deleted,
-    // and their state is meaningless.
-    if (!kv.second->HasChannels()) {
-      continue;
-    }
-    any_receiving = any_receiving || kv.second->any_channel_receiving();
-    any_failed = any_failed || kv.second->AnyChannelFailed();
-    all_connected = all_connected && kv.second->all_channels_writable();
-    all_completed = all_completed && kv.second->AllChannelsCompleted();
+  bool all_done_gathering = !channels_.empty();
+  for (const auto& channel : channels_) {
+    any_receiving = any_receiving || channel->receiving();
+    any_failed = any_failed ||
+                 channel->GetState() == TransportChannelState::STATE_FAILED;
+    all_connected = all_connected && channel->writable();
+    all_completed =
+        all_completed && channel->writable() &&
+        channel->GetState() == TransportChannelState::STATE_COMPLETED &&
+        channel->GetIceRole() == ICEROLE_CONTROLLING &&
+        channel->gathering_state() == kIceGatheringComplete;
     any_gathering =
-        any_gathering || kv.second->gathering_state() != kIceGatheringNew;
+        any_gathering || channel->gathering_state() != kIceGatheringNew;
     all_done_gathering = all_done_gathering &&
-                         kv.second->gathering_state() == kIceGatheringComplete;
+                         channel->gathering_state() == kIceGatheringComplete;
   }
 
   if (any_failed) {
@@ -562,13 +602,4 @@
   }
 }
 
-bool TransportController::HasChannels_w() {
-  for (const auto& kv : transports_) {
-    if (kv.second->HasChannels()) {
-      return true;
-    }
-  }
-  return false;
-}
-
 }  // namespace cricket
diff --git a/p2p/base/transportcontroller.h b/p2p/base/transportcontroller.h
index f506e01..45fcfea 100644
--- a/p2p/base/transportcontroller.h
+++ b/p2p/base/transportcontroller.h
@@ -81,9 +81,14 @@
   bool ReadyForRemoteCandidates(const std::string& transport_name);
   bool GetStats(const std::string& transport_name, TransportStats* stats);
 
+  // Creates a channel if it doesn't exist. Otherwise, increments a reference
+  // count and returns an existing channel.
   virtual TransportChannel* CreateTransportChannel_w(
       const std::string& transport_name,
       int component);
+
+  // Decrements a channel's reference count, and destroys the channel if
+  // nothing is referencing it.
   virtual void DestroyTransportChannel_w(const std::string& transport_name,
                                          int component);
 
@@ -121,6 +126,33 @@
  private:
   void OnMessage(rtc::Message* pmsg) override;
 
+  // It's the Transport that's currently responsible for creating/destroying
+  // channels, but the TransportController keeps track of how many external
+  // objects (BaseChannels) reference each channel.
+  struct RefCountedChannel {
+    RefCountedChannel() : impl_(nullptr), ref_(0) {}
+    explicit RefCountedChannel(TransportChannelImpl* impl)
+        : impl_(impl), ref_(0) {}
+
+    void AddRef() { ++ref_; }
+    void DecRef() {
+      ASSERT(ref_ > 0);
+      --ref_;
+    }
+    int ref() const { return ref_; }
+
+    TransportChannelImpl* get() const { return impl_; }
+    TransportChannelImpl* operator->() const { return impl_; }
+
+   private:
+    TransportChannelImpl* impl_;
+    int ref_;
+  };
+
+  std::vector<RefCountedChannel>::iterator FindChannel_w(
+      const std::string& transport_name,
+      int component);
+
   Transport* GetOrCreateTransport_w(const std::string& transport_name);
   void DestroyTransport_w(const std::string& transport_name);
   void DestroyAllTransports_w();
@@ -152,29 +184,27 @@
   bool GetStats_w(const std::string& transport_name, TransportStats* stats);
 
   // Handlers for signals from Transport.
-  void OnTransportConnecting_w(Transport* transport);
-  void OnTransportWritableState_w(Transport* transport);
-  void OnTransportReceivingState_w(Transport* transport);
-  void OnTransportCompleted_w(Transport* transport);
-  void OnTransportFailed_w(Transport* transport);
-  void OnTransportGatheringState_w(Transport* transport);
-  void OnTransportCandidatesGathered_w(
-      Transport* transport,
-      const std::vector<Candidate>& candidates);
-  void OnTransportRoleConflict_w();
+  void OnChannelWritableState_w(TransportChannel* channel);
+  void OnChannelReceivingState_w(TransportChannel* channel);
+  void OnChannelGatheringState_w(TransportChannelImpl* channel);
+  void OnChannelCandidateGathered_w(TransportChannelImpl* channel,
+                                    const Candidate& candidate);
+  void OnChannelRoleConflict_w(TransportChannelImpl* channel);
+  void OnChannelConnectionRemoved_w(TransportChannelImpl* channel);
 
   void UpdateAggregateStates_w();
-  bool HasChannels_w();
 
   rtc::Thread* const signaling_thread_ = nullptr;
   rtc::Thread* const worker_thread_ = nullptr;
   typedef std::map<std::string, Transport*> TransportMap;
   TransportMap transports_;
 
+  std::vector<RefCountedChannel> channels_;
+
   PortAllocator* const port_allocator_ = nullptr;
   rtc::SSLProtocolVersion ssl_max_version_ = rtc::SSL_PROTOCOL_DTLS_10;
 
-  // Aggregate state for Transports
+  // Aggregate state for TransportChannelImpls.
   IceConnectionState connection_state_ = kIceConnectionConnecting;
   bool receiving_ = false;
   IceGatheringState gathering_state_ = kIceGatheringNew;