Add FakeVideoDecoder.

media/filters/fake_demuxer_stream.h

Index: media/filters/fake_demuxer_stream.h
diff --git a/media/filters/fake_demuxer_stream.h b/media/filters/fake_demuxer_stream.h
index 1b20ba7b6c36657575a2dbd3032cbd03c34a5326..4cb2a829d86b495b25302217ed67d6e25430fdc9 100644
--- a/media/filters/fake_demuxer_stream.h
+++ b/media/filters/fake_demuxer_stream.h
@@ -35,6 +35,8 @@ class MEDIA_EXPORT FakeDemuxerStream : public DemuxerStream {
   virtual Type type() OVERRIDE;
   virtual void EnableBitstreamConverter() OVERRIDE;
 
+  int num_buffers_returned() const { return num_buffers_returned_; }
+
   // Upon the next read, holds the read callback until SatisfyRead() or Reset()
   // is called.
   void HoldNextRead();
@@ -59,6 +61,8 @@ class MEDIA_EXPORT FakeDemuxerStream : public DemuxerStream {
   // Number of frames left with the current decoder config.
   int num_buffers_left_in_current_config_;
 
+  int num_buffers_returned_;
+
   base::TimeDelta current_timestamp_;
   base::TimeDelta duration_;