Aura Window Capture: Ensure capture callback is always run.

content/browser/media/capture/aura_window_capture_machine.cc

Index: content/browser/media/capture/aura_window_capture_machine.cc
diff --git a/content/browser/media/capture/aura_window_capture_machine.cc b/content/browser/media/capture/aura_window_capture_machine.cc
index b959e153f658f60d03d379ce17e639b5e910b28e..daaa5cc0758d62e4a895ddab5dfd37d395318048 100644
--- a/content/browser/media/capture/aura_window_capture_machine.cc
+++ b/content/browser/media/capture/aura_window_capture_machine.cc
@@ -199,7 +199,7 @@ void AuraWindowCaptureMachine::DidCopyOutput(
 
   static bool first_call = true;
 
-  bool succeeded = ProcessCopyOutputResponse(
+  const bool succeeded = ProcessCopyOutputResponse(
       video_frame, start_time, capture_frame_cb, std::move(result));
 
   base::TimeDelta capture_time = base::TimeTicks::Now() - start_time;
@@ -223,6 +223,11 @@ void AuraWindowCaptureMachine::DidCopyOutput(
                                          : FIRST_WINDOW_CAPTURE_FAILED);
     }
   }
+
+  // If ProcessCopyOutputResponse() failed, it will not run |capture_frame_cb|,
+  // so do that now.
+  if (!succeeded)
+    capture_frame_cb.Run(video_frame, start_time, false);

[GeorgeZ, 2016/04/23 18:47:15]

There is one more loop hole in 
https://code.google.com/p/chromium/codesearch#chromium/src/media/capture/cont...

frame_number = oracle_.RecordCapture(attenuated_utilization); leads to
num_frames_pending_++;

Callback leads to num_frames_pending_--;

if (!(*storage))
    return false;

leads to num_frames_pending_++ and there is no valid call_back.

[miu, 2016/04/26 02:27:58]

Done.  Good catch.

 }
 
 bool AuraWindowCaptureMachine::ProcessCopyOutputResponse(
@@ -310,8 +315,11 @@ void AuraWindowCaptureMachine::CopyOutputFinishedForVideo(
   if (machine) {
     if (machine->cursor_renderer_ && result)
       machine->cursor_renderer_->RenderOnVideoFrame(target);
-    capture_frame_cb.Run(target, start_time, result);
+  } else {
+    result = false;
   }
+
+  capture_frame_cb.Run(target, start_time, result);

[GeorgeZ, 2016/04/23 18:47:15]

You may add a check for result (bool success) in void
ThreadSafeCaptureOracle::DidCaptureFrame() instead of doing it in
oracle_.CompleteCapture. I think do check earlier makes more sensor.

[miu, 2016/04/26 02:27:58]

VideoCaptureOracle::CompleteCapture() must be called regardless of success/fail,
and ThreadSafeCaptureOracle checks the return value from that call to determine
whether to proceed with delivering the video frame to the client.  So, I don't
see how the check could be any sooner than it is.

 }
 
 void AuraWindowCaptureMachine::OnWindowBoundsChanged(