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

remoting/host/client_session.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef REMOTING_HOST_CLIENT_SESSION_H_
 #define REMOTING_HOST_CLIENT_SESSION_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 26 matching lines @@
 
 namespace remoting {
 
 class AudioPump;
 class DesktopEnvironment;
 class DesktopEnvironmentFactory;
 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 {
    public:
     // Called after authentication has started.
     virtual void OnSessionAuthenticating(ClientSession* client) = 0;
 
     // Called after authentication has finished successfully.
     virtual void OnSessionAuthenticated(ClientSession* client) = 0;
 
@@ skipping 41 matching lines @@
   void SetCapabilities(const protocol::Capabilities& capabilities) override;
   void RequestPairing(
       const remoting::protocol::PairingRequest& pairing_request) override;
   void DeliverClientMessage(const protocol::ExtensionMessage& message) override;
 
   // protocol::ConnectionToClient::EventHandler interface.
   void OnConnectionAuthenticating(
       protocol::ConnectionToClient* connection) override;
   void OnConnectionAuthenticated(
       protocol::ConnectionToClient* connection) override;
+  void OnCreateVideoStreams(protocol::ConnectionToClient* connection) override;
   void OnConnectionChannelsConnected(
       protocol::ConnectionToClient* connection) override;
   void OnConnectionClosed(protocol::ConnectionToClient* connection,
                           protocol::ErrorCode error) override;
   void OnInputEventReceived(protocol::ConnectionToClient* connection,
                             int64_t timestamp) override;
   void OnRouteChange(protocol::ConnectionToClient* connection,
                      const std::string& channel_name,
                      const protocol::TransportRoute& route) override;
 
@@ skipping 94 matching lines @@
   scoped_ptr<HostExtensionSessionManager> extension_manager_;
 
   // Set to true if the client was authenticated successfully.
   bool is_authenticated_;
 
   // Used to store video channel pause & lossless parameters.
   bool pause_video_;
   bool lossless_video_encode_;
   bool lossless_video_color_;
 
+  // VideoLayout is sent only after the capabilities are negotiated with the
+  // client. Until then it's stored in |pending_video_layout_message_|.

[Jamie, 2016/04/04 18:21:47]

Maybe expand on this a bit to explain why the message can't be sent until then
(since it's not conditional on what the capabilities are). If you think that's
too much detail for the header, maybe move it to the implementation.

Is it a client-side limitation, and if so can it be fixed there?

[Sergey Ulanov, 2016/04/05 21:21:54]

My thinking was that in the future we may need to change the format of that
messages depending on the capabilities. But looking at this today, I don't think
we really need this right now, so I removed this requirement. In any case the
message can be sent only after control channel is connected, so we still need
this variable.
No, it's not client-side limitation.

+  scoped_ptr<protocol::VideoLayout> pending_video_layout_message_;
+
   // Used to disable callbacks to |this| once DisconnectSession() has been
   // called.
   base::WeakPtrFactory<ClientSessionControl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ClientSession);
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_HOST_CLIENT_SESSION_H_