ScreenCapturerWinDirectx may flicker on certain hardware

webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc

 /*
  *  Copyright (c) 2016 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 201 matching lines @@
   }
 
   if (last_frame_) {
     // No change since last frame or AcquireNextFrame() timed out, we will
     // export last frame to the target.
     for (DesktopRegion::Iterator it(updated_region); !it.IsAtEnd();
          it.Advance()) {
       target->CopyPixelsFrom(*last_frame_, it.rect().top_left(), it.rect());
     }
     target->mutable_updated_region()->AddRegion(updated_region);
+  } else {
+    // If we were at the very first frame, and capturing failed, the
+    // context->updated_region should be kept unchanged for next attempt.
+    context->updated_region.Swap(&updated_region);
   }
   // If AcquireNextFrame() failed with timeout error, we do not need to release
   // the frame.
   return error.Error() == DXGI_ERROR_WAIT_TIMEOUT || ReleaseFrame();
 }
 
 DesktopRect DxgiOutputDuplicator::TranslatedDesktopRect(DesktopVector offset) {
   DesktopRect result(DesktopRect::MakeSize(desktop_rect_.size()));
   result.Translate(offset);
   return result;
@@ skipping 126 matching lines @@
 }
 
 int64_t DxgiOutputDuplicator::num_frames_captured() const {
 #if !defined(NDEBUG)
   RTC_DCHECK_EQ(!!last_frame_, num_frames_captured_ > 0);
 #endif
   return num_frames_captured_;
 }
 
 }  // namespace webrtc