Update XServerPixelBuffer to handle shmget() errors properly.

webrtc/modules/desktop_capture/x11/x_server_pixel_buffer.h

 /*
  *  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 40 matching lines @@
   // beginning.
   void Synchronize();
 
   // Capture the specified rectangle and stores it in the |frame|. In the case
   // 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().
   bool CaptureRect(const DesktopRect& rect, DesktopFrame* frame);
 
  private:
+  void ReleaseSharedMemorySegment();
+
   void InitShm(const XWindowAttributes& attributes);
   bool InitPixmaps(int depth);
 
   // We expose two forms of blitting to handle variations in the pixel format.
   // In FastBlit(), the operation is effectively a memcpy.
   void FastBlit(uint8_t* image,
                 const DesktopRect& rect,
                 DesktopFrame* frame);
   void SlowBlit(uint8_t* image,
                 const DesktopRect& rect,
                 DesktopFrame* frame);
 
   Display* display_ = nullptr;
   Window window_ = 0;
   DesktopSize window_size_;
   XImage* x_image_ = nullptr;
   XShmSegmentInfo* shm_segment_info_ = nullptr;
   Pixmap shm_pixmap_ = 0;
   GC shm_gc_ = nullptr;
   bool xshm_get_image_succeeded_ = false;
 
   RTC_DISALLOW_COPY_AND_ASSIGN(XServerPixelBuffer);
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_DESKTOP_CAPTURE_X11_X_SERVER_PIXEL_BUFFER_H_