Fix error handling in X11 screen capturer

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 322 matching lines @@
 
     for (DesktopRegion::Iterator it(*updated_region);
          !it.IsAtEnd(); it.Advance()) {
       if (!x_server_pixel_buffer_.CaptureRect(it.rect(), frame.get()))
         return nullptr;
     }
   } else {
     // Doing full-screen polling, or this is the first capture after a
     // screen-resolution change.  In either case, need a full-screen capture.
     DesktopRect screen_rect = DesktopRect::MakeSize(frame->size());
-    x_server_pixel_buffer_.CaptureRect(screen_rect, frame.get());
+    if (!x_server_pixel_buffer_.CaptureRect(screen_rect, frame.get()))
+      return nullptr;
     updated_region->SetRect(screen_rect);
   }
 
   return std::move(frame);
 }
 
 void ScreenCapturerLinux::ScreenConfigurationChanged() {
   // Make sure the frame buffers will be reallocated.
   queue_.Reset();
 
@@ skipping 55 matching lines @@
 
   std::unique_ptr<ScreenCapturerLinux> capturer(new ScreenCapturerLinux());
   if (!capturer.get()->Init(options)) {
     return nullptr;
   }
 
   return std::move(capturer);
 }
 
 }  // namespace webrtc