media: Fix a GpuVideoDecoder initialization crash on Android

media/filters/gpu_video_decoder.h

Index: media/filters/gpu_video_decoder.h
diff --git a/media/filters/gpu_video_decoder.h b/media/filters/gpu_video_decoder.h
index 1f999cbe0ffe8de3f7ea341ea187b6702768df61..4095375667aabc3744426b53d258c7a91c6c26ee 100644
--- a/media/filters/gpu_video_decoder.h
+++ b/media/filters/gpu_video_decoder.h
@@ -178,6 +178,9 @@ class MEDIA_EXPORT GpuVideoDecoder
   // occurs.
   std::unique_ptr<VideoDecodeAccelerator> vda_;
 
+  // Whether |vda_->Initialize()| has been called.

[sandersd (OOO until July 31), 2017/01/11 21:39:58]

This is accurate, but hard to interpret with regards to the async initialize
process. Recommend expanding this text to explain that in more detail.

+  bool vda_initialized_;
+
   InitCB init_cb_;
   OutputCB output_cb_;