Update XServerPixelBuffer to handle errors returned from XGetImage().

webrtc/modules/desktop_capture/x11/x_server_pixel_buffer.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 213 matching lines @@
 void XServerPixelBuffer::Synchronize() {
   if (shm_segment_info_ && !shm_pixmap_) {
     // XShmGetImage can fail if the display is being reconfigured.
     XErrorTrap error_trap(display_);
     // XShmGetImage fails if the window is partially out of screen.
     xshm_get_image_succeeded_ =
         XShmGetImage(display_, window_, x_image_, 0, 0, AllPlanes);
   }
 }
 
-void XServerPixelBuffer::CaptureRect(const DesktopRect& rect,
+bool XServerPixelBuffer::CaptureRect(const DesktopRect& rect,
                                      DesktopFrame* frame) {
   assert(rect.right() <= window_size_.width());
   assert(rect.bottom() <= window_size_.height());
 
   uint8_t* data;
 
   if (shm_segment_info_ && (shm_pixmap_ || xshm_get_image_succeeded_)) {
     if (shm_pixmap_) {
       XCopyArea(display_, window_, shm_pixmap_, shm_gc_,
                 rect.left(), rect.top(), rect.width(), rect.height(),
                 rect.left(), rect.top());
       XSync(display_, False);
     }
     data = reinterpret_cast<uint8_t*>(x_image_->data) +
         rect.top() * x_image_->bytes_per_line +
         rect.left() * x_image_->bits_per_pixel / 8;
   } else {
     if (x_image_)
       XDestroyImage(x_image_);
     x_image_ = XGetImage(display_, window_, rect.left(), rect.top(),
                          rect.width(), rect.height(), AllPlanes, ZPixmap);
+    if (!x_image_)
+      return false;
+
     data = reinterpret_cast<uint8_t*>(x_image_->data);
   }
 
   if (IsXImageRGBFormat(x_image_)) {
     FastBlit(data, rect, frame);
   } else {
     SlowBlit(data, rect, frame);
   }
+
+  return true;
 }
 
 void XServerPixelBuffer::FastBlit(uint8_t* image,
                                   const DesktopRect& rect,
                                   DesktopFrame* frame) {
   uint8_t* src_pos = image;
   int src_stride = x_image_->bytes_per_line;
   int dst_x = rect.left(), dst_y = rect.top();
 
   uint8_t* dst_pos = frame->data() + frame->stride() * dst_y;
@@ skipping 52 matching lines @@
       // Write as 32-bit RGB.
       dst_pos_32[x] = ((r >> 8) & 0xff0000) | ((g >> 16) & 0xff00) |
           ((b >> 24) & 0xff);
     }
     dst_pos += frame->stride();
     src_pos += src_stride;
   }
 }
 
 }  // namespace webrtc