Fix WebRTC transport to use single offer-answer exchange instead of two.

remoting/host/client_session.h

Index: remoting/host/client_session.h
diff --git a/remoting/host/client_session.h b/remoting/host/client_session.h
index 0caf5e10ff326c5a96a646da80d90174ccfc2bef..ed95a98a999d94f29b946bd9309838e7de9fd4e6 100644
--- a/remoting/host/client_session.h
+++ b/remoting/host/client_session.h
@@ -44,13 +44,16 @@ class InputInjector;
 class MouseShapePump;
 class ScreenControls;
 
+namespace protocol {
+class VideoLayout;
+}  // namespace protocol
+
 // A ClientSession keeps a reference to a connection to a client, and maintains
 // per-client state.
-class ClientSession
-    : public base::NonThreadSafe,
-      public protocol::HostStub,
-      public protocol::ConnectionToClient::EventHandler,
-      public ClientSessionControl {
+class ClientSession : public base::NonThreadSafe,
+                      public protocol::HostStub,
+                      public protocol::ConnectionToClient::EventHandler,
+                      public ClientSessionControl {
  public:
   // Callback interface for passing events to the ChromotingHost.
   class EventHandler {
@@ -112,6 +115,7 @@ class ClientSession
       protocol::ConnectionToClient* connection) override;
   void OnConnectionAuthenticated(
       protocol::ConnectionToClient* connection) override;
+  void CreateVideoStreams(protocol::ConnectionToClient* connection) override;
   void OnConnectionChannelsConnected(
       protocol::ConnectionToClient* connection) override;
   void OnConnectionClosed(protocol::ConnectionToClient* connection,
@@ -219,12 +223,19 @@ class ClientSession
   scoped_ptr<HostExtensionSessionManager> extension_manager_;
 
   // Set to true if the client was authenticated successfully.
-  bool is_authenticated_;
+  bool is_authenticated_ = false;
+
+  // Set to true after all data channels have been connected.
+  bool channels_connected_ = false;
 
   // Used to store video channel pause & lossless parameters.
-  bool pause_video_;
-  bool lossless_video_encode_;
-  bool lossless_video_color_;
+  bool pause_video_ = false;
+  bool lossless_video_encode_ = false;
+  bool lossless_video_color_ = false;
+
+  // VideoLayout is sent only after the control channel is connected. Until
+  // then it's stored in |pending_video_layout_message_|.
+  scoped_ptr<protocol::VideoLayout> pending_video_layout_message_;

[Jamie, 2016/04/05 21:46:36]

Optional: Would it be better to queue this in the client stub instead of here?
The fact that this is sent over the control channel seems like an implementation
detail that this class shouldn't have to care about. In fact, it seems like
there might be any number of messages that may need to be queued pending
connection establishment, and they could be queued in a generic way at an
appropriate layer.

[Sergey Ulanov, 2016/04/06 21:23:50]

That's a great suggestions. Queuing actually works for all stubs when using
IceConnection objects (which use BufferedSocketWriter internally), but not for
WebRTC connections. I've added TODO.

 
   // Used to disable callbacks to |this| once DisconnectSession() has been
   // called.