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

remoting/host/ipc_desktop_environment.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_IPC_DESKTOP_ENVIRONMENT_H_
 #define REMOTING_HOST_IPC_DESKTOP_ENVIRONMENT_H_
 
 #include <map>
 #include <string>
 
@@ skipping 34 matching lines @@
       base::WeakPtr<DesktopSessionConnector> desktop_session_connector,
       bool virtual_terminal);
   virtual ~IpcDesktopEnvironment();
 
   // DesktopEnvironment implementation.
   virtual scoped_ptr<AudioCapturer> CreateAudioCapturer(
       scoped_refptr<base::SingleThreadTaskRunner> audio_task_runner) OVERRIDE;
   virtual scoped_ptr<EventExecutor> CreateEventExecutor(
       scoped_refptr<base::SingleThreadTaskRunner> input_task_runner,
       scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner) OVERRIDE;
+  virtual scoped_ptr<SessionController> CreateSessionController() OVERRIDE;
   virtual scoped_ptr<media::ScreenCapturer> CreateVideoCapturer(
       scoped_refptr<base::SingleThreadTaskRunner> capture_task_runner,
       scoped_refptr<base::SingleThreadTaskRunner> encode_task_runner) OVERRIDE;
 
  private:
   // Task runner on which public methods of this class should be called.
   scoped_refptr<base::SingleThreadTaskRunner> caller_task_runner_;
 
   scoped_refptr<DesktopSessionProxy> desktop_session_proxy_;
 
@@ skipping 61 matching lines @@
   // This gives us more than 67 years of unique IDs assuming a new ID is
   // allocated every second.
   int next_id_;
 
   DISALLOW_COPY_AND_ASSIGN(IpcDesktopEnvironmentFactory);
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_HOST_IPC_DESKTOP_ENVIRONMENT_H_