Allow GCC 4.9 to compile Chromium

webrtc/modules/desktop_capture/screen_capturer_x11.cc

 /*
  *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 394 matching lines @@
 std::unique_ptr<DesktopCapturer> DesktopCapturer::CreateRawScreenCapturer(
     const DesktopCaptureOptions& options) {
   if (!options.x_display())
     return nullptr;
 
   std::unique_ptr<ScreenCapturerLinux> capturer(new ScreenCapturerLinux());
   if (!capturer.get()->Init(options)) {
     return nullptr;
   }
 
-  return capturer;
+  return std::move(capturer);
 }
 
 }  // namespace webrtc