Reland the CL to remove candidates when doing continual gathering When doing candidate re-gathering in the same ICE generation, signal the remote side to remove its remote candidates. Fixed the pure virtual method in jsep.h BUG= R=glaznev@webrtc.org, pthatcher@webrtc.org Review URL: https://codereview.webrtc.org/1788703003 . Cr-Commit-Position: refs/heads/master@{#11985}

diff --git a/webrtc/api/androidtests/src/org/webrtc/PeerConnectionTest.java b/webrtc/api/androidtests/src/org/webrtc/PeerConnectionTest.java
index bbaa152..ff98d7d 100644
--- a/webrtc/api/androidtests/src/org/webrtc/PeerConnectionTest.java
+++ b/webrtc/api/androidtests/src/org/webrtc/PeerConnectionTest.java

@@ -109,6 +109,9 @@
       }
     }
 
+    @Override
+    public void onIceCandidatesRemoved(IceCandidate[] candidates) {}
+
     public synchronized void setExpectedResolution(int width, int height) {
       expectedWidth = width;
       expectedHeight = height;

diff --git a/webrtc/api/java/jni/peerconnection_jni.cc b/webrtc/api/java/jni/peerconnection_jni.cc
index 2e3cb0a..d614ed6 100644
--- a/webrtc/api/java/jni/peerconnection_jni.cc
+++ b/webrtc/api/java/jni/peerconnection_jni.cc

@@ -56,6 +56,7 @@
 #include "webrtc/api/rtpreceiverinterface.h"
 #include "webrtc/api/rtpsenderinterface.h"
 #include "webrtc/api/videosourceinterface.h"
+#include "webrtc/api/webrtcsdp.h"
 #include "webrtc/base/bind.h"
 #include "webrtc/base/checks.h"
 #include "webrtc/base/event_tracer.h"
@@ -195,8 +196,8 @@
         "<init>", "(Ljava/lang/String;ILjava/lang/String;)V");
     jstring j_mid = JavaStringFromStdString(jni(), candidate->sdp_mid());
     jstring j_sdp = JavaStringFromStdString(jni(), sdp);
-    jobject j_candidate = jni()->NewObject(
-        candidate_class, ctor, j_mid, candidate->sdp_mline_index(), j_sdp);
+    jobject j_candidate = jni()->NewObject(candidate_class, ctor, j_mid,
+                                           candidate->sdp_mline_index(), j_sdp);
     CHECK_EXCEPTION(jni()) << "error during NewObject";
     jmethodID m = GetMethodID(jni(), *j_observer_class_,
                               "onIceCandidate", "(Lorg/webrtc/IceCandidate;)V");
@@ -204,6 +205,17 @@
     CHECK_EXCEPTION(jni()) << "error during CallVoidMethod";
   }
 
+  void OnIceCandidatesRemoved(
+      const std::vector<cricket::Candidate>& candidates) {
+    ScopedLocalRefFrame local_ref_frame(jni());
+    jobjectArray candidates_array = ToJavaCandidateArray(jni(), candidates);
+    jmethodID m =
+        GetMethodID(jni(), *j_observer_class_, "onIceCandidatesRemoved",
+                    "([Lorg/webrtc/IceCandidate;)V");
+    jni()->CallVoidMethod(*j_observer_global_, m, candidates_array);
+    CHECK_EXCEPTION(jni()) << "Error during CallVoidMethod";
+  }
+
   void OnSignalingChange(
       PeerConnectionInterface::SignalingState new_state) override {
     ScopedLocalRefFrame local_ref_frame(jni());
@@ -371,6 +383,36 @@
     DeleteGlobalRef(jni(), j_stream);
   }
 
+  jobject ToJavaCandidate(JNIEnv* jni,
+                          jclass* candidate_class,
+                          const cricket::Candidate& candidate) {
+    std::string sdp = webrtc::SdpSerializeCandidate(candidate);
+    RTC_CHECK(!sdp.empty()) << "got an empty ICE candidate";
+    jmethodID ctor = GetMethodID(jni, *candidate_class, "<init>",
+                                 "(Ljava/lang/String;ILjava/lang/String;)V");
+    jstring j_mid = JavaStringFromStdString(jni, candidate.transport_name());
+    jstring j_sdp = JavaStringFromStdString(jni, sdp);
+    // sdp_mline_index is not used, pass an invalid value -1.
+    jobject j_candidate =
+        jni->NewObject(*candidate_class, ctor, j_mid, -1, j_sdp);
+    CHECK_EXCEPTION(jni) << "error during Java Candidate NewObject";
+    return j_candidate;
+  }
+
+  jobjectArray ToJavaCandidateArray(
+      JNIEnv* jni,
+      const std::vector<cricket::Candidate>& candidates) {
+    jclass candidate_class = FindClass(jni, "org/webrtc/IceCandidate");
+    jobjectArray java_candidates =
+        jni->NewObjectArray(candidates.size(), candidate_class, NULL);
+    int i = 0;
+    for (const cricket::Candidate& candidate : candidates) {
+      jobject j_candidate = ToJavaCandidate(jni, &candidate_class, candidate);
+      jni->SetObjectArrayElement(java_candidates, i++, j_candidate);
+    }
+    return java_candidates;
+  }
+
   JNIEnv* jni() {
     return AttachCurrentThreadIfNeeded();
   }
@@ -1718,6 +1760,35 @@
   return ExtractNativePC(jni, j_pc)->AddIceCandidate(candidate.get());
 }
 
+static cricket::Candidate GetCandidateFromJava(JNIEnv* jni,
+                                               jobject j_candidate) {
+  jclass j_candidate_class = GetObjectClass(jni, j_candidate);
+  jfieldID j_sdp_mid_id =
+      GetFieldID(jni, j_candidate_class, "sdpMid", "Ljava/lang/String;");
+  std::string sdp_mid =
+      JavaToStdString(jni, GetStringField(jni, j_candidate, j_sdp_mid_id));
+  jfieldID j_sdp_id =
+      GetFieldID(jni, j_candidate_class, "sdp", "Ljava/lang/String;");
+  std::string sdp =
+      JavaToStdString(jni, GetStringField(jni, j_candidate, j_sdp_id));
+  cricket::Candidate candidate;
+  if (!webrtc::SdpDeserializeCandidate(sdp_mid, sdp, &candidate, NULL)) {
+    LOG(LS_ERROR) << "SdpDescrializeCandidate failed with sdp " << sdp;
+  }
+  return candidate;
+}
+
+JOW(jboolean, PeerConnection_nativeRemoveIceCandidates)
+(JNIEnv* jni, jobject j_pc, jobjectArray j_candidates) {
+  std::vector<cricket::Candidate> candidates;
+  size_t num_candidates = jni->GetArrayLength(j_candidates);
+  for (size_t i = 0; i < num_candidates; ++i) {
+    jobject j_candidate = jni->GetObjectArrayElement(j_candidates, i);
+    candidates.push_back(GetCandidateFromJava(jni, j_candidate));
+  }
+  return ExtractNativePC(jni, j_pc)->RemoveIceCandidates(candidates);
+}
+
 JOW(jboolean, PeerConnection_nativeAddLocalStream)(
     JNIEnv* jni, jobject j_pc, jlong native_stream) {
   return ExtractNativePC(jni, j_pc)->AddStream(

diff --git a/webrtc/api/java/src/org/webrtc/PeerConnection.java b/webrtc/api/java/src/org/webrtc/PeerConnection.java
index 3c9fa0e..5f52619 100644
--- a/webrtc/api/java/src/org/webrtc/PeerConnection.java
+++ b/webrtc/api/java/src/org/webrtc/PeerConnection.java

@@ -58,6 +58,9 @@
     /** Triggered when a new ICE candidate has been found. */
     public void onIceCandidate(IceCandidate candidate);
 
+    /** Triggered when some ICE candidates have been removed. */
+    public void onIceCandidatesRemoved(IceCandidate[] candidates);
+
     /** Triggered when media is received on a new stream from remote peer. */
     public void onAddStream(MediaStream stream);
 
@@ -193,6 +196,10 @@
         candidate.sdpMid, candidate.sdpMLineIndex, candidate.sdp);
   }
 
+  public boolean removeIceCandidates(final IceCandidate[] candidates) {
+    return nativeRemoveIceCandidates(candidates);
+  }
+
   public boolean addStream(MediaStream stream) {
     boolean ret = nativeAddLocalStream(stream.nativeStream);
     if (!ret) {
@@ -273,6 +280,8 @@
   private native boolean nativeAddIceCandidate(
       String sdpMid, int sdpMLineIndex, String iceCandidateSdp);
 
+  private native boolean nativeRemoveIceCandidates(final IceCandidate[] candidates);
+
   private native boolean nativeAddLocalStream(long nativeStream);
 
   private native void nativeRemoveLocalStream(long nativeStream);

diff --git a/webrtc/api/jsep.h b/webrtc/api/jsep.h
index 0673ce1..e11a2ad 100644
--- a/webrtc/api/jsep.h
+++ b/webrtc/api/jsep.h

@@ -20,8 +20,8 @@
 #include "webrtc/base/refcount.h"
 
 namespace cricket {
-class SessionDescription;
 class Candidate;
+class SessionDescription;
 }  // namespace cricket
 
 namespace webrtc {
@@ -95,6 +95,11 @@
   // Returns false if the session description does not have a media section that
   // corresponds to the |candidate| label.
   virtual bool AddCandidate(const IceCandidateInterface* candidate) = 0;
+  // Removes the candidates from the description.
+  // Returns the number of candidates removed.
+  virtual size_t RemoveCandidates(
+      const std::vector<cricket::Candidate>& candidates) { return 0; }
+
   // Returns the number of m- lines in the session description.
   virtual size_t number_of_mediasections() const = 0;
   // Returns a collection of all candidates that belong to a certain m-line

diff --git a/webrtc/api/jsepicecandidate.cc b/webrtc/api/jsepicecandidate.cc
index 2aabcb8..cced1b4 100644
--- a/webrtc/api/jsepicecandidate.cc
+++ b/webrtc/api/jsepicecandidate.cc

@@ -79,4 +79,17 @@
   return ret;
 }
 
+size_t JsepCandidateCollection::remove(const cricket::Candidate& candidate) {
+  auto iter = std::find_if(candidates_.begin(), candidates_.end(),
+                           [candidate](JsepIceCandidate* c) {
+                             return candidate.MatchesForRemoval(c->candidate());
+                           });
+  if (iter != candidates_.end()) {
+    delete *iter;
+    candidates_.erase(iter);
+    return 1;
+  }
+  return 0;
+}
+
 }  // namespace webrtc

diff --git a/webrtc/api/jsepicecandidate.h b/webrtc/api/jsepicecandidate.h
index 529b2a7..7e9500b 100644
--- a/webrtc/api/jsepicecandidate.h
+++ b/webrtc/api/jsepicecandidate.h

@@ -70,6 +70,9 @@
   virtual const IceCandidateInterface* at(size_t index) const {
     return candidates_[index];
   }
+  // Removes the candidate that has a matching address and protocol.
+  // Returns the number of candidates that were removed.
+  size_t remove(const cricket::Candidate& candidate);
 
  private:
   std::vector<JsepIceCandidate*> candidates_;

diff --git a/webrtc/api/jsepsessiondescription.cc b/webrtc/api/jsepsessiondescription.cc
index b47114b..eb776c8 100644
--- a/webrtc/api/jsepsessiondescription.cc
+++ b/webrtc/api/jsepsessiondescription.cc

@@ -137,6 +137,20 @@
   return true;
 }
 
+size_t JsepSessionDescription::RemoveCandidates(
+    const std::vector<cricket::Candidate>& candidates) {
+  size_t num_removed = 0;
+  for (auto& candidate : candidates) {
+    int mediasection_index = GetMediasectionIndex(candidate);
+    if (mediasection_index < 0) {
+      // Not found.
+      continue;
+    }
+    num_removed += candidate_collection_[mediasection_index].remove(candidate);
+  }
+  return num_removed;
+}
+
 size_t JsepSessionDescription::number_of_mediasections() const {
   if (!description_)
     return 0;
@@ -184,4 +198,16 @@
   return true;
 }
 
+int JsepSessionDescription::GetMediasectionIndex(
+    const cricket::Candidate& candidate) {
+  // Find the description with a matching transport name of the candidate.
+  const std::string& transport_name = candidate.transport_name();
+  for (size_t i = 0; i < description_->contents().size(); ++i) {
+    if (transport_name == description_->contents().at(i).name) {
+      return static_cast<int>(i);
+    }
+  }
+  return -1;
+}
+
 }  // namespace webrtc

diff --git a/webrtc/api/jsepsessiondescription.h b/webrtc/api/jsepsessiondescription.h
index 244ee19..9a0d873 100644
--- a/webrtc/api/jsepsessiondescription.h
+++ b/webrtc/api/jsepsessiondescription.h

@@ -19,6 +19,7 @@
 #include "webrtc/api/jsep.h"
 #include "webrtc/api/jsepicecandidate.h"
 #include "webrtc/base/scoped_ptr.h"
+#include "webrtc/p2p/base/candidate.h"
 
 namespace cricket {
 class SessionDescription;
@@ -57,6 +58,8 @@
   // Allow changing the type. Used for testing.
   void set_type(const std::string& type) { type_ = type; }
   virtual bool AddCandidate(const IceCandidateInterface* candidate);
+  virtual size_t RemoveCandidates(
+      const std::vector<cricket::Candidate>& candidates);
   virtual size_t number_of_mediasections() const;
   virtual const IceCandidateCollection* candidates(
       size_t mediasection_index) const;
@@ -80,6 +83,7 @@
 
   bool GetMediasectionIndex(const IceCandidateInterface* candidate,
                             size_t* index);
+  int GetMediasectionIndex(const cricket::Candidate& candidate);
 
   RTC_DISALLOW_COPY_AND_ASSIGN(JsepSessionDescription);
 };

diff --git a/webrtc/api/jsepsessiondescription_unittest.cc b/webrtc/api/jsepsessiondescription_unittest.cc
index 7868bea..3d87513 100644
--- a/webrtc/api/jsepsessiondescription_unittest.cc
+++ b/webrtc/api/jsepsessiondescription_unittest.cc

@@ -109,7 +109,7 @@
   EXPECT_EQ(2u, jsep_desc_->number_of_mediasections());
 }
 
-// Test that we can add a candidate to a session description.
+// Test that we can add a candidate to a session description without MID.
 TEST_F(JsepSessionDescriptionTest, AddCandidateWithoutMid) {
   JsepIceCandidate jsep_candidate("", 0, candidate_);
   EXPECT_TRUE(jsep_desc_->AddCandidate(&jsep_candidate));
@@ -125,9 +125,12 @@
   EXPECT_EQ(0u, jsep_desc_->candidates(1)->count());
 }
 
-TEST_F(JsepSessionDescriptionTest, AddCandidateWithMid) {
+// Test that we can add and remove candidates to a session description with
+// MID. Removing candidates requires MID (transport_name).
+TEST_F(JsepSessionDescriptionTest, AddAndRemoveCandidatesWithMid) {
   // mid and m-line index don't match, in this case mid is preferred.
-  JsepIceCandidate jsep_candidate("video", 0, candidate_);
+  std::string mid = "video";
+  JsepIceCandidate jsep_candidate(mid, 0, candidate_);
   EXPECT_TRUE(jsep_desc_->AddCandidate(&jsep_candidate));
   EXPECT_EQ(0u, jsep_desc_->candidates(0)->count());
   const IceCandidateCollection* ice_candidates = jsep_desc_->candidates(1);
@@ -140,6 +143,12 @@
   EXPECT_TRUE(ice_candidate->candidate().IsEquivalent(candidate_));
   // The mline index should have been updated according to mid.
   EXPECT_EQ(1, ice_candidate->sdp_mline_index());
+
+  std::vector<cricket::Candidate> candidates(1, candidate_);
+  candidates[0].set_transport_name(mid);
+  EXPECT_EQ(1u, jsep_desc_->RemoveCandidates(candidates));
+  EXPECT_EQ(0u, jsep_desc_->candidates(0)->count());
+  EXPECT_EQ(0u, jsep_desc_->candidates(1)->count());
 }
 
 TEST_F(JsepSessionDescriptionTest, AddCandidateAlreadyHasUfrag) {

diff --git a/webrtc/api/peerconnection.cc b/webrtc/api/peerconnection.cc
index e4ab40e..54e76d4 100644
--- a/webrtc/api/peerconnection.cc
+++ b/webrtc/api/peerconnection.cc

@@ -1205,6 +1205,12 @@
   return session_->ProcessIceMessage(ice_candidate);
 }
 
+bool PeerConnection::RemoveIceCandidates(
+    const std::vector<cricket::Candidate>& candidates) {
+  TRACE_EVENT0("webrtc", "PeerConnection::RemoveIceCandidates");
+  return session_->RemoveRemoteIceCandidates(candidates);
+}
+
 void PeerConnection::RegisterUMAObserver(UMAObserver* observer) {
   TRACE_EVENT0("webrtc", "PeerConnection::RegisterUmaObserver");
   uma_observer_ = observer;
@@ -1384,6 +1390,12 @@
   observer_->OnIceCandidate(candidate);
 }
 
+void PeerConnection::OnIceCandidatesRemoved(
+    const std::vector<cricket::Candidate>& candidates) {
+  RTC_DCHECK(signaling_thread()->IsCurrent());
+  observer_->OnIceCandidatesRemoved(candidates);
+}
+
 void PeerConnection::OnIceConnectionReceivingChange(bool receiving) {
   RTC_DCHECK(signaling_thread()->IsCurrent());
   observer_->OnIceConnectionReceivingChange(receiving);

diff --git a/webrtc/api/peerconnection.h b/webrtc/api/peerconnection.h
index 3b0d558..d715ecd 100644
--- a/webrtc/api/peerconnection.h
+++ b/webrtc/api/peerconnection.h

@@ -132,6 +132,8 @@
   bool SetConfiguration(
       const PeerConnectionInterface::RTCConfiguration& config) override;
   bool AddIceCandidate(const IceCandidateInterface* candidate) override;
+  bool RemoveIceCandidates(
+      const std::vector<cricket::Candidate>& candidates) override;
 
   void RegisterUMAObserver(UMAObserver* observer) override;
 
@@ -187,6 +189,8 @@
   void OnIceConnectionChange(IceConnectionState new_state) override;
   void OnIceGatheringChange(IceGatheringState new_state) override;
   void OnIceCandidate(const IceCandidateInterface* candidate) override;
+  void OnIceCandidatesRemoved(
+      const std::vector<cricket::Candidate>& candidates) override;
   void OnIceConnectionReceivingChange(bool receiving) override;
 
   // Signals from WebRtcSession.

diff --git a/webrtc/api/peerconnectioninterface.h b/webrtc/api/peerconnectioninterface.h
index f6c8cba..22109c4 100644
--- a/webrtc/api/peerconnectioninterface.h
+++ b/webrtc/api/peerconnectioninterface.h

@@ -439,6 +439,12 @@
   // take the ownership of the |candidate|.
   virtual bool AddIceCandidate(const IceCandidateInterface* candidate) = 0;
 
+  // Removes a group of remote candidates from the ICE agent.
+  virtual bool RemoveIceCandidates(
+      const std::vector<cricket::Candidate>& candidates) {
+    return false;
+  }
+
   virtual void RegisterUMAObserver(UMAObserver* observer) = 0;
 
   // Returns the current SignalingState.
@@ -495,6 +501,12 @@
   // New Ice candidate have been found.
   virtual void OnIceCandidate(const IceCandidateInterface* candidate) = 0;
 
+  // Ice candidates have been removed.
+  // TODO(honghaiz): Make this a pure virtual method when all its subclasses
+  // implement it.
+  virtual void OnIceCandidatesRemoved(
+      const std::vector<cricket::Candidate>& candidates) {}
+
   // Called when the ICE connection receiving status changes.
   virtual void OnIceConnectionReceivingChange(bool receiving) {}
 

diff --git a/webrtc/api/peerconnectionproxy.h b/webrtc/api/peerconnectionproxy.h
index e47bc96..1183e61 100644
--- a/webrtc/api/peerconnectionproxy.h
+++ b/webrtc/api/peerconnectionproxy.h

@@ -66,6 +66,9 @@
                 SetConfiguration,
                 const PeerConnectionInterface::RTCConfiguration&);
   PROXY_METHOD1(bool, AddIceCandidate, const IceCandidateInterface*)
+  PROXY_METHOD1(bool,
+                RemoveIceCandidates,
+                const std::vector<cricket::Candidate>&);
   PROXY_METHOD1(void, RegisterUMAObserver, UMAObserver*)
   PROXY_METHOD0(SignalingState, signaling_state)
   PROXY_METHOD0(IceState, ice_state)

diff --git a/webrtc/api/webrtcsdp.cc b/webrtc/api/webrtcsdp.cc
index 54bb059..4a296d9 100644
--- a/webrtc/api/webrtcsdp.cc
+++ b/webrtc/api/webrtcsdp.cc

@@ -154,8 +154,7 @@
 // Candidate
 static const char kCandidateHost[] = "host";
 static const char kCandidateSrflx[] = "srflx";
-// TODO: How to map the prflx with circket candidate type
-// static const char kCandidatePrflx[] = "prflx";
+static const char kCandidatePrflx[] = "prflx";
 static const char kCandidateRelay[] = "relay";
 static const char kTcpCandidateType[] = "tcptype";
 
@@ -871,11 +870,14 @@
 
 // Serializes the passed in IceCandidateInterface to a SDP string.
 // candidate - The candidate to be serialized.
-std::string SdpSerializeCandidate(
-    const IceCandidateInterface& candidate) {
+std::string SdpSerializeCandidate(const IceCandidateInterface& candidate) {
+  return SdpSerializeCandidate(candidate.candidate());
+}
+
+// Serializes a cricket Candidate.
+std::string SdpSerializeCandidate(const cricket::Candidate& candidate) {
   std::string message;
-  std::vector<cricket::Candidate> candidates;
-  candidates.push_back(candidate.candidate());
+  std::vector<cricket::Candidate> candidates(1, candidate);
   BuildCandidate(candidates, true, &message);
   // From WebRTC draft section 4.8.1.1 candidate-attribute will be
   // just candidate:<candidate> not a=candidate:<blah>CRLF
@@ -938,6 +940,18 @@
   return true;
 }
 
+bool SdpDeserializeCandidate(const std::string& transport_name,
+                             const std::string& message,
+                             cricket::Candidate* candidate,
+                             SdpParseError* error) {
+  ASSERT(candidate != nullptr);
+  if (!ParseCandidate(message, candidate, error, true)) {
+    return false;
+  }
+  candidate->set_transport_name(transport_name);
+  return true;
+}
+
 bool ParseCandidate(const std::string& message, Candidate* candidate,
                     SdpParseError* error, bool is_raw) {
   ASSERT(candidate != NULL);
@@ -1026,6 +1040,8 @@
     candidate_type = cricket::STUN_PORT_TYPE;
   } else if (type == kCandidateRelay) {
     candidate_type = cricket::RELAY_PORT_TYPE;
+  } else if (type == kCandidatePrflx) {
+    candidate_type = cricket::PRFLX_PORT_TYPE;
   } else {
     return ParseFailed(first_line, "Unsupported candidate type.", error);
   }
@@ -1761,6 +1777,9 @@
       type = kCandidateSrflx;
     } else if (it->type() == cricket::RELAY_PORT_TYPE) {
       type = kCandidateRelay;
+    } else if (it->type() == cricket::PRFLX_PORT_TYPE) {
+      type = kCandidatePrflx;
+      // Peer reflexive candidate may be signaled for being removed.
     } else {
       ASSERT(false);
       // Never write out candidates if we don't know the type.

diff --git a/webrtc/api/webrtcsdp.h b/webrtc/api/webrtcsdp.h
index 2b22b62..e7fdb34 100644
--- a/webrtc/api/webrtcsdp.h
+++ b/webrtc/api/webrtcsdp.h

@@ -22,8 +22,11 @@
 
 #include <string>
 
-namespace webrtc {
+namespace cricket {
+class Candidate;
+}  // namespace cricket
 
+namespace webrtc {
 class IceCandidateInterface;
 class JsepIceCandidate;
 class JsepSessionDescription;
@@ -42,6 +45,10 @@
 // candidate - The candidate to be serialized.
 std::string SdpSerializeCandidate(const IceCandidateInterface& candidate);
 
+// Serializes a cricket Candidate.
+// candidate - The candidate to be serialized.
+std::string SdpSerializeCandidate(const cricket::Candidate& candidate);
+
 // Deserializes the passed in SDP string to a JsepSessionDescription.
 // message - SDP string to be Deserialized.
 // jdesc - The JsepSessionDescription deserialized from the SDP string.
@@ -61,6 +68,20 @@
 bool SdpDeserializeCandidate(const std::string& message,
                              JsepIceCandidate* candidate,
                              SdpParseError* error);
+
+// Deserializes the passed in SDP string to a cricket Candidate.
+// The first line must be a=candidate line and only the first line will be
+// parsed.
+// transport_name - The transport name (MID) of the candidate.
+// message - The SDP string to be deserialized.
+// candidate - The cricket Candidate from the SDP string.
+// error - The detail error information when parsing fails.
+// return - true on success, false on failure.
+bool SdpDeserializeCandidate(const std::string& transport_name,
+                             const std::string& message,
+                             cricket::Candidate* candidate,
+                             SdpParseError* error);
+
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_WEBRTCSDP_H_

diff --git a/webrtc/api/webrtcsession.cc b/webrtc/api/webrtcsession.cc
index 9ed5640..3d9b6fb 100644
--- a/webrtc/api/webrtcsession.cc
+++ b/webrtc/api/webrtcsession.cc

@@ -501,6 +501,8 @@
       this, &WebRtcSession::OnTransportControllerGatheringState);
   transport_controller_->SignalCandidatesGathered.connect(
       this, &WebRtcSession::OnTransportControllerCandidatesGathered);
+  transport_controller_->SignalCandidatesRemoved.connect(
+      this, &WebRtcSession::OnTransportControllerCandidatesRemoved);
 }
 
 WebRtcSession::~WebRtcSession() {
@@ -1086,7 +1088,7 @@
   if (!remote_desc_) {
     LOG(LS_ERROR) << "ProcessIceMessage: ICE candidates can't be added "
                   << "without any remote session description.";
-     return false;
+    return false;
   }
 
   if (!candidate) {
@@ -1114,6 +1116,35 @@
   }
 }
 
+bool WebRtcSession::RemoveRemoteIceCandidates(
+    const std::vector<cricket::Candidate>& candidates) {
+  if (!remote_desc_) {
+    LOG(LS_ERROR) << "RemoveRemoteIceCandidates: ICE candidates can't be "
+                  << "removed without any remote session description.";
+    return false;
+  }
+
+  if (candidates.empty()) {
+    LOG(LS_ERROR) << "RemoveRemoteIceCandidates: candidates are empty.";
+    return false;
+  }
+
+  size_t number_removed = remote_desc_->RemoveCandidates(candidates);
+  if (number_removed != candidates.size()) {
+    LOG(LS_ERROR) << "RemoveRemoteIceCandidates: Failed to remove candidates. "
+                  << "Requested " << candidates.size() << " but only "
+                  << number_removed << " are removed.";
+  }
+
+  // Remove the candidates from the transport controller.
+  std::string error;
+  bool res = transport_controller_->RemoveRemoteCandidates(candidates, &error);
+  if (!res && !error.empty()) {
+    LOG(LS_ERROR) << "Error when removing remote candidates: " << error;
+  }
+  return true;
+}
+
 bool WebRtcSession::SetIceTransports(
     PeerConnectionInterface::IceTransportsType type) {
   return port_allocator()->set_candidate_filter(
@@ -1523,6 +1554,27 @@
   }
 }
 
+void WebRtcSession::OnTransportControllerCandidatesRemoved(
+    const std::vector<cricket::Candidate>& candidates) {
+  ASSERT(signaling_thread()->IsCurrent());
+  // Sanity check.
+  for (const cricket::Candidate& candidate : candidates) {
+    if (candidate.transport_name().empty()) {
+      LOG(LS_ERROR) << "OnTransportControllerCandidatesRemoved: "
+                    << "empty content name in candidate "
+                    << candidate.ToString();
+      return;
+    }
+  }
+
+  if (local_desc_) {
+    local_desc_->RemoveCandidates(candidates);
+  }
+  if (ice_observer_) {
+    ice_observer_->OnIceCandidatesRemoved(candidates);
+  }
+}
+
 // Enabling voice and video channel.
 void WebRtcSession::EnableChannels() {
   if (voice_channel_ && !voice_channel_->enabled())
@@ -1582,14 +1634,11 @@
   return ret;
 }
 
-bool WebRtcSession::UseCandidate(
-    const IceCandidateInterface* candidate) {
-
+bool WebRtcSession::UseCandidate(const IceCandidateInterface* candidate) {
   size_t mediacontent_index = static_cast<size_t>(candidate->sdp_mline_index());
   size_t remote_content_size = remote_desc_->description()->contents().size();
   if (mediacontent_index >= remote_content_size) {
-    LOG(LS_ERROR)
-        << "UseRemoteCandidateInSession: Invalid candidate media index.";
+    LOG(LS_ERROR) << "UseCandidate: Invalid candidate media index.";
     return false;
   }
 
@@ -1930,8 +1979,8 @@
   size_t remote_content_size =
       current_remote_desc->description()->contents().size();
   if (mediacontent_index >= remote_content_size) {
-    LOG(LS_ERROR)
-        << "ReadyToUseRemoteCandidate: Invalid candidate media index.";
+    LOG(LS_ERROR) << "ReadyToUseRemoteCandidate: Invalid candidate media index "
+                  << mediacontent_index;
 
     *valid = false;
     return false;

diff --git a/webrtc/api/webrtcsession.h b/webrtc/api/webrtcsession.h
index 27472c9..9495116 100644
--- a/webrtc/api/webrtcsession.h
+++ b/webrtc/api/webrtcsession.h

@@ -25,6 +25,7 @@
 #include "webrtc/base/sslidentity.h"
 #include "webrtc/base/thread.h"
 #include "webrtc/media/base/mediachannel.h"
+#include "webrtc/p2p/base/candidate.h"
 #include "webrtc/p2p/base/transportcontroller.h"
 #include "webrtc/pc/mediasession.h"
 
@@ -81,6 +82,10 @@
   // New Ice candidate have been found.
   virtual void OnIceCandidate(const IceCandidateInterface* candidate) = 0;
 
+  // Some local ICE candidates have been removed.
+  virtual void OnIceCandidatesRemoved(
+      const std::vector<cricket::Candidate>& candidates) = 0;
+
   // Called whenever the state changes between receiving and not receiving.
   virtual void OnIceConnectionReceivingChange(bool receiving) {}
 
@@ -205,6 +210,9 @@
                             std::string* err_desc);
   bool ProcessIceMessage(const IceCandidateInterface* ice_candidate);
 
+  bool RemoveRemoteIceCandidates(
+      const std::vector<cricket::Candidate>& candidates);
+
   bool SetIceTransports(PeerConnectionInterface::IceTransportsType type);
 
   cricket::IceConfig ParseIceConfig(
@@ -431,7 +439,9 @@
   void OnTransportControllerGatheringState(cricket::IceGatheringState state);
   void OnTransportControllerCandidatesGathered(
       const std::string& transport_name,
-      const cricket::Candidates& candidates);
+      const std::vector<cricket::Candidate>& candidates);
+  void OnTransportControllerCandidatesRemoved(
+      const std::vector<cricket::Candidate>& candidates);
 
   std::string GetSessionErrorMsg();
 

diff --git a/webrtc/api/webrtcsession_unittest.cc b/webrtc/api/webrtcsession_unittest.cc
index 2c9a99b..c0fff52 100644
--- a/webrtc/api/webrtcsession_unittest.cc
+++ b/webrtc/api/webrtcsession_unittest.cc

@@ -189,11 +189,18 @@
     EXPECT_NE(PeerConnectionInterface::kIceGatheringNew, ice_gathering_state_);
   }
 
+  // Some local candidates are removed.
+  void OnIceCandidatesRemoved(
+      const std::vector<cricket::Candidate>& candidates) {
+    num_candidates_removed_ += candidates.size();
+  }
+
   bool oncandidatesready_;
   std::vector<cricket::Candidate> mline_0_candidates_;
   std::vector<cricket::Candidate> mline_1_candidates_;
   PeerConnectionInterface::IceConnectionState ice_connection_state_;
   PeerConnectionInterface::IceGatheringState ice_gathering_state_;
+  size_t num_candidates_removed_ = 0;
 };
 
 class WebRtcSessionForTest : public webrtc::WebRtcSession {
@@ -358,6 +365,9 @@
   void AddInterface(const SocketAddress& addr) {
     network_manager_.AddInterface(addr);
   }
+  void RemoveInterface(const SocketAddress& addr) {
+    network_manager_.RemoveInterface(addr);
+  }
 
   // If |dtls_identity_store| != null or |rtc_configuration| contains
   // |certificates| then DTLS will be enabled unless explicitly disabled by
@@ -2106,12 +2116,14 @@
       "Called in wrong state: STATE_INIT", answer);
 }
 
-TEST_F(WebRtcSessionTest, TestAddRemoteCandidate) {
+// Tests that the remote candidates are added and removed successfully.
+TEST_F(WebRtcSessionTest, TestAddAndRemoveRemoteCandidates) {
   Init();
   SendAudioVideoStream1();
 
-  cricket::Candidate candidate;
-  candidate.set_component(1);
+  cricket::Candidate candidate(1, "udp", rtc::SocketAddress("1.1.1.1", 5000), 0,
+                               "", "", "host", 0, "");
+  candidate.set_transport_name("audio");
   JsepIceCandidate ice_candidate1(kMediaContentName0, 0, candidate);
 
   // Fail since we have not set a remote description.
@@ -2129,6 +2141,7 @@
 
   EXPECT_TRUE(session_->ProcessIceMessage(&ice_candidate1));
   candidate.set_component(2);
+  candidate.set_address(rtc::SocketAddress("2.2.2.2", 6000));
   JsepIceCandidate ice_candidate2(kMediaContentName0, 0, candidate);
   EXPECT_TRUE(session_->ProcessIceMessage(&ice_candidate2));
 
@@ -2154,9 +2167,16 @@
 
   JsepIceCandidate bad_ice_candidate("bad content name", 99, candidate);
   EXPECT_FALSE(session_->ProcessIceMessage(&bad_ice_candidate));
+
+  // Remove candidate1 and candidate2
+  std::vector<cricket::Candidate> remote_candidates;
+  remote_candidates.push_back(ice_candidate1.candidate());
+  remote_candidates.push_back(ice_candidate2.candidate());
+  EXPECT_TRUE(session_->RemoveRemoteIceCandidates(remote_candidates));
+  EXPECT_EQ(0u, candidates->count());
 }
 
-// Test that a remote candidate is added to the remote session description and
+// Tests that a remote candidate is added to the remote session description and
 // that it is retained if the remote session description is changed.
 TEST_F(WebRtcSessionTest, TestRemoteCandidatesAddedToSessionDescription) {
   Init();
@@ -2209,8 +2229,11 @@
 }
 
 // Test that local candidates are added to the local session description and
-// that they are retained if the local session description is changed.
-TEST_F(WebRtcSessionTest, TestLocalCandidatesAddedToSessionDescription) {
+// that they are retained if the local session description is changed. And if
+// continual gathering is enabled, they are removed from the local session
+// description when the network is down.
+TEST_F(WebRtcSessionTest,
+       TestLocalCandidatesAddedAndRemovedIfGatherContinually) {
   AddInterface(rtc::SocketAddress(kClientAddrHost1, kClientAddrPort));
   Init();
   SendAudioVideoStream1();
@@ -2243,6 +2266,43 @@
   candidates = local_desc->candidates(1);
   ASSERT_TRUE(candidates != NULL);
   EXPECT_EQ(0u, candidates->count());
+
+  candidates = local_desc->candidates(kMediaContentIndex0);
+  size_t num_local_candidates = candidates->count();
+  // Enable Continual Gathering
+  session_->SetIceConfig(cricket::IceConfig(-1, -1, true, false, -1));
+  // Bring down the network interface to trigger candidate removals.
+  RemoveInterface(rtc::SocketAddress(kClientAddrHost1, kClientAddrPort));
+  // Verify that all local candidates are removed.
+  EXPECT_EQ(0, observer_.num_candidates_removed_);
+  EXPECT_EQ_WAIT(num_local_candidates, observer_.num_candidates_removed_,
+                 kIceCandidatesTimeout);
+  EXPECT_EQ_WAIT(0u, candidates->count(), kIceCandidatesTimeout);
+}
+
+// Tests that if continual gathering is disabled, local candidates won't be
+// removed when the interface is turned down.
+TEST_F(WebRtcSessionTest, TestLocalCandidatesNotRemovedIfNotGatherContinually) {
+  AddInterface(rtc::SocketAddress(kClientAddrHost1, kClientAddrPort));
+  Init();
+  SendAudioVideoStream1();
+  CreateAndSetRemoteOfferAndLocalAnswer();
+
+  const SessionDescriptionInterface* local_desc = session_->local_description();
+  const IceCandidateCollection* candidates =
+      local_desc->candidates(kMediaContentIndex0);
+  ASSERT_TRUE(candidates != NULL);
+  EXPECT_TRUE_WAIT(observer_.oncandidatesready_, kIceCandidatesTimeout);
+
+  size_t num_local_candidates = candidates->count();
+  EXPECT_LT(0u, num_local_candidates);
+  // By default, Continual Gathering is disabled.
+  // Bring down the network interface.
+  RemoveInterface(rtc::SocketAddress(kClientAddrHost1, kClientAddrPort));
+  // Verify that the local candidates are not removed.
+  rtc::Thread::Current()->ProcessMessages(1000);
+  EXPECT_EQ(0, observer_.num_candidates_removed_);
+  EXPECT_EQ(num_local_candidates, candidates->count());
 }
 
 // Test that we can set a remote session description with remote candidates.