Update XServerPixelBuffer to handle errors returned from XGetImage().

webrtc/modules/desktop_capture/x11/x_server_pixel_buffer.h

Index: webrtc/modules/desktop_capture/x11/x_server_pixel_buffer.h
diff --git a/webrtc/modules/desktop_capture/x11/x_server_pixel_buffer.h b/webrtc/modules/desktop_capture/x11/x_server_pixel_buffer.h
index b202abb9bc005d488aba83ec09e56c9ef94126f0..2a177c4ff77a67a28c784ea0578a29e24977de7e 100644
--- a/webrtc/modules/desktop_capture/x11/x_server_pixel_buffer.h
+++ b/webrtc/modules/desktop_capture/x11/x_server_pixel_buffer.h
@@ -55,7 +55,7 @@ class XServerPixelBuffer {
   // where the full-screen data is captured by Synchronize(), this simply
   // returns the pointer without doing any more work. The caller must ensure
   // that |rect| is not larger than window_size().
-  void CaptureRect(const DesktopRect& rect, DesktopFrame* frame);
+  bool CaptureRect(const DesktopRect& rect, DesktopFrame* frame);
 
  private:
   void InitShm(const XWindowAttributes& attributes);