cc: Video layers without a frame should not occlude

cc/layers/video_frame_provider_client_impl.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layers/video_frame_provider_client_impl.h"
 
 #include "base/trace_event/trace_event.h"
 #include "cc/base/math_util.h"
 #include "cc/layers/video_layer_impl.h"
 #include "media/base/video_frame.h"
@@ skipping 80 matching lines @@
   provider_lock_.AssertAcquired();
   provider_->PutCurrentFrame();
 }
 
 void VideoFrameProviderClientImpl::ReleaseLock() {
   DCHECK(thread_checker_.CalledOnValidThread());
   provider_lock_.AssertAcquired();
   provider_lock_.Release();
 }
 
+bool VideoFrameProviderClientImpl::HasCurrentFrame() {
+  base::AutoLock locker(provider_lock_);
+  return provider_ && provider_->GetCurrentFrame();

[danakj, 2015/05/18 17:19:52]

You need to match calls to GetCurrentFrame() with PutCurrentFrame(), but I think
it might be nicer to add a HasCurrentFrame() to the VideoFrameProvider as well.
Or is that horrible?

[hendrikw, 2015/05/18 17:46:58]

That's an weird requirement.  WebMediaPlayerMS::GetCurrentFrame changes state :/
 I don't like. I'll add the HasCurrentFrame() to the provider.

+}
+
 const gfx::Transform& VideoFrameProviderClientImpl::StreamTextureMatrix()
     const {
   DCHECK(thread_checker_.CalledOnValidThread());
   return stream_texture_matrix_;
 }
 
 void VideoFrameProviderClientImpl::StopUsingProvider() {
   // Block the provider from shutting down until this client is done
   // using the frame.
   base::AutoLock locker(provider_lock_);
@@ skipping 54 matching lines @@
   if (!provider_ ||
       !provider_->UpdateCurrentFrame(args.frame_time + args.interval,
                                      args.frame_time + 2 * args.interval)) {
     return;
   }
 
   DidReceiveFrame();
 }
 
 }  // namespace cc