Fix DesktopSessioAgent crash when handling nullptr OnCaptureCompleted callback.

remoting/host/desktop_session_agent.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_DESKTOP_SESSION_AGENT_H_
 #define REMOTING_HOST_DESKTOP_SESSION_AGENT_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 164 matching lines @@
   // Used to apply client-requested changes in screen resolution.
   std::unique_ptr<ScreenControls> screen_controls_;
 
   // IPC channel connecting the desktop process with the network process.
   std::unique_ptr<IPC::ChannelProxy> network_channel_;
 
   // The client end of the network-to-desktop pipe. It is kept alive until
   // the network process connects to the pipe.
   base::File desktop_pipe_;
 
-  // Size of the most recent captured video frame.
-  webrtc::DesktopSize current_size_;
-
   // True if the desktop session agent has been started.
   bool started_ = false;
 
   // Captures the screen.
   std::unique_ptr<webrtc::DesktopCapturer> video_capturer_;
 
   // Captures mouse shapes.
   std::unique_ptr<webrtc::MouseCursorMonitor> mouse_cursor_monitor_;
 
   // Keep reference to the last frame sent to make sure shared buffer is alive
   // before it's received.
   std::unique_ptr<webrtc::DesktopFrame> last_frame_;
 
   // Used to disable callbacks to |this|.
   base::WeakPtrFactory<DesktopSessionAgent> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DesktopSessionAgent);
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_HOST_DESKTOP_SESSION_AGENT_H_