cc: Video layers without a frame should not occlude

cc/layers/video_frame_provider_client_impl.cc

Index: cc/layers/video_frame_provider_client_impl.cc
diff --git a/cc/layers/video_frame_provider_client_impl.cc b/cc/layers/video_frame_provider_client_impl.cc
index 5fab4e2f04c4d0cc01dc081ccc59a0a86e79880a..ed2b90007bf287338d56bbab3805d9973e85d3a6 100644
--- a/cc/layers/video_frame_provider_client_impl.cc
+++ b/cc/layers/video_frame_provider_client_impl.cc
@@ -98,6 +98,11 @@ void VideoFrameProviderClientImpl::ReleaseLock() {
   provider_lock_.Release();
 }
 
+bool VideoFrameProviderClientImpl::HasCurrentFrame() {
+  base::AutoLock locker(provider_lock_);
+  return provider_ && provider_->HasCurrentFrame();
+}
+
 const gfx::Transform& VideoFrameProviderClientImpl::StreamTextureMatrix()
     const {
   DCHECK(thread_checker_.CalledOnValidThread());