ResizingHostObserver is created by the desktop environment together with other stubs.

remoting/host/ipc_desktop_environment.cc

 // 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.
 
 #include "remoting/host/ipc_desktop_environment.h"
 
 #include <utility>
 
 #include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "base/process_util.h"
 #include "base/single_thread_task_runner.h"
 #include "ipc/ipc_sender.h"
 #include "media/video/capture/screen/screen_capturer.h"
 #include "remoting/host/audio_capturer.h"
 #include "remoting/host/chromoting_messages.h"
 #include "remoting/host/desktop_session.h"
 #include "remoting/host/desktop_session_proxy.h"
 #include "remoting/host/event_executor.h"
+#include "remoting/host/session_controller.h"
 
 namespace remoting {
 
 IpcDesktopEnvironment::IpcDesktopEnvironment(
     scoped_refptr<base::SingleThreadTaskRunner> caller_task_runner,
     scoped_refptr<base::SingleThreadTaskRunner> io_task_runner,
     const std::string& client_jid,
     const base::Closure& disconnect_callback,
     base::WeakPtr<DesktopSessionConnector> desktop_session_connector,
     bool virtual_terminal)
@@ skipping 21 matching lines @@
 
 scoped_ptr<EventExecutor> IpcDesktopEnvironment::CreateEventExecutor(
     scoped_refptr<base::SingleThreadTaskRunner> input_task_runner,
     scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner) {
   DCHECK(caller_task_runner_->BelongsToCurrentThread());
 
   return desktop_session_proxy_->CreateEventExecutor(input_task_runner,
                                                      ui_task_runner);
 }
 
+scoped_ptr<SessionController> IpcDesktopEnvironment::CreateSessionController() {
+  DCHECK(caller_task_runner_->BelongsToCurrentThread());
+
+  ConnectToDesktopSession();

[Jamie, 2013/03/09 00:53:18]

Why is this call needed for CreateSessionController but not for any of the other
Create* methods?

[alexeypa (please no reviews), 2013/03/09 01:05:34]

It is not needed. I guess I didn't pick one of fixes when I was preparing the
patch.

+  return desktop_session_proxy_->CreateSessionController();
+}
+
 scoped_ptr<media::ScreenCapturer> IpcDesktopEnvironment::CreateVideoCapturer(
     scoped_refptr<base::SingleThreadTaskRunner> capture_task_runner,
     scoped_refptr<base::SingleThreadTaskRunner> encode_task_runner) {
   DCHECK(caller_task_runner_->BelongsToCurrentThread());
 
   return desktop_session_proxy_->CreateVideoCapturer(capture_task_runner,
                                                      encode_task_runner);
 }
 
 IpcDesktopEnvironmentFactory::IpcDesktopEnvironmentFactory(
@@ skipping 107 matching lines @@
   if (i != active_connections_.end()) {
     DesktopSessionProxy* desktop_session_proxy = i->second;
     active_connections_.erase(i);
 
     // Disconnect the client session.
     desktop_session_proxy->DisconnectSession();
   }
 }
 
 }  // namespace remoting