Revert "Move webrtc/{base => rtc_base}" (https://codereview.webrtc.org/2877023002)

Will reland in two different commits to preserve git blame history.

BUG=webrtc:7634
NOTRY=True
TBR=kwiberg@webrtc.org

Change-Id: I550da8525aeb9c5b8f96338fcf1c9714f3dcdab1
Reviewed-on: https://chromium-review.googlesource.com/554610
Reviewed-by: Henrik Kjellander <kjellander@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#18820}
diff --git a/webrtc/base/asyncsocket.h b/webrtc/base/asyncsocket.h
index 9c97139..6dc41b6 100644
--- a/webrtc/base/asyncsocket.h
+++ b/webrtc/base/asyncsocket.h
@@ -11,9 +11,73 @@
 #ifndef WEBRTC_BASE_ASYNCSOCKET_H_
 #define WEBRTC_BASE_ASYNCSOCKET_H_
 
+#include "webrtc/base/sigslot.h"
+#include "webrtc/base/socket.h"
 
-// This header is deprecated and is just left here temporarily during
-// refactoring. See https://bugs.webrtc.org/7634 for more details.
-#include "webrtc/rtc_base/asyncsocket.h"
+namespace rtc {
+
+// TODO: Remove Socket and rename AsyncSocket to Socket.
+
+// Provides the ability to perform socket I/O asynchronously.
+class AsyncSocket : public Socket {
+ public:
+  AsyncSocket();
+  ~AsyncSocket() override;
+
+  AsyncSocket* Accept(SocketAddress* paddr) override = 0;
+
+  // SignalReadEvent and SignalWriteEvent use multi_threaded_local to allow
+  // access concurrently from different thread.
+  // For example SignalReadEvent::connect will be called in AsyncUDPSocket ctor
+  // but at the same time the SocketDispatcher maybe signaling the read event.
+  // ready to read
+  sigslot::signal1<AsyncSocket*,
+                   sigslot::multi_threaded_local> SignalReadEvent;
+  // ready to write
+  sigslot::signal1<AsyncSocket*,
+                   sigslot::multi_threaded_local> SignalWriteEvent;
+  sigslot::signal1<AsyncSocket*> SignalConnectEvent;     // connected
+  sigslot::signal2<AsyncSocket*, int> SignalCloseEvent;  // closed
+};
+
+class AsyncSocketAdapter : public AsyncSocket, public sigslot::has_slots<> {
+ public:
+  // The adapted socket may explicitly be null, and later assigned using Attach.
+  // However, subclasses which support detached mode must override any methods
+  // that will be called during the detached period (usually GetState()), to
+  // avoid dereferencing a null pointer.
+  explicit AsyncSocketAdapter(AsyncSocket* socket);
+  ~AsyncSocketAdapter() override;
+  void Attach(AsyncSocket* socket);
+  SocketAddress GetLocalAddress() const override;
+  SocketAddress GetRemoteAddress() const override;
+  int Bind(const SocketAddress& addr) override;
+  int Connect(const SocketAddress& addr) override;
+  int Send(const void* pv, size_t cb) override;
+  int SendTo(const void* pv, size_t cb, const SocketAddress& addr) override;
+  int Recv(void* pv, size_t cb, int64_t* timestamp) override;
+  int RecvFrom(void* pv,
+               size_t cb,
+               SocketAddress* paddr,
+               int64_t* timestamp) override;
+  int Listen(int backlog) override;
+  AsyncSocket* Accept(SocketAddress* paddr) override;
+  int Close() override;
+  int GetError() const override;
+  void SetError(int error) override;
+  ConnState GetState() const override;
+  int GetOption(Option opt, int* value) override;
+  int SetOption(Option opt, int value) override;
+
+ protected:
+  virtual void OnConnectEvent(AsyncSocket* socket);
+  virtual void OnReadEvent(AsyncSocket* socket);
+  virtual void OnWriteEvent(AsyncSocket* socket);
+  virtual void OnCloseEvent(AsyncSocket* socket, int err);
+
+  AsyncSocket* socket_;
+};
+
+}  // namespace rtc
 
 #endif  // WEBRTC_BASE_ASYNCSOCKET_H_