Revert 121055 - Remove BeginSessionDeprecated.

remoting/protocol/client_control_dispatcher.cc

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 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.
 
 #include "remoting/protocol/client_control_dispatcher.h"
 
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/message_loop_proxy.h"
 #include "net/socket/stream_socket.h"
 #include "remoting/base/constants.h"
@@ skipping 18 matching lines @@
 void ClientControlDispatcher::OnInitialized() {
   // TODO(garykac): Set write failed callback.
   writer_->Init(channel(), BufferedSocketWriter::WriteFailedCallback());
   reader_.Init(channel(), base::Bind(
       &ClientControlDispatcher::OnMessageReceived, base::Unretained(this)));
 }
 
 void ClientControlDispatcher::OnMessageReceived(
     ControlMessage* message, const base::Closure& done_task) {
   DCHECK(client_stub_);
+
   base::ScopedClosureRunner done_runner(done_task);
-  LOG(WARNING) << "Unknown control message received.";
+
+  if (message->has_begin_session_deprecated()) {
+    // Host sends legacy BeginSession message for compatibility with
+    // older clients. Ignore it without warning.
+  } else {
+    LOG(WARNING) << "Unknown control message received.";
+  }
 }
 
 }  // namespace protocol
 }  // namespace remoting