Add AudioBufferStream.

media/filters/fake_video_decoder.cc

Index: media/filters/fake_video_decoder.cc
diff --git a/media/filters/fake_video_decoder.cc b/media/filters/fake_video_decoder.cc
index f3c4ef112d765173aed83226ed57f2835470b1e0..d8658c80c8cfeeab50a0efc14bf5ac3e679eb165 100644
--- a/media/filters/fake_video_decoder.cc
+++ b/media/filters/fake_video_decoder.cc
@@ -18,7 +18,8 @@ FakeVideoDecoder::FakeVideoDecoder(int decoding_delay)
       weak_factory_(this),
       decoding_delay_(decoding_delay),
       state_(UNINITIALIZED),
-      total_bytes_decoded_(0) {
+      total_bytes_decoded_(0),
+      reads_queued_(0) {
   DCHECK_GE(decoding_delay, 0);
 }
 
@@ -103,6 +104,19 @@ void FakeVideoDecoder::Stop(const base::Closure& closure) {
   DoStop();
 }
 
+scoped_refptr<VideoFrame> FakeVideoDecoder::GetDecodeOutput() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  if (!reads_queued_) {
+    return NULL;
+  }

[xhwang, 2014/03/06 23:32:40]

nit: no need for braces.

+  --reads_queued_;
+  return VideoFrame::CreateEOSFrame();

[xhwang, 2014/03/06 23:32:40]

This isn't quite right. Even though this decoder is a fake, it tries to be as
real as possible. An EOS frame in the middle of the decoding process is not real
:)

Actually we may not need to do anything to "queue read". FakeVideoDecoder
supports decoding delay, which will actually queue decoded frames internally.
GetDecodeOutput() can directly return those frames.

One problem with this is that we'll always drain the decoder before trying new
decodes. In reality, all of our video decoders don't support GetDecodeOutput().
So it's still worth testing the case where FakeVideoDecoder::GetDecodeOutput()
always return NULL. 

Can we change the ctor of FakeVideoDecoder to
FakeVideoDecoder(int decoding_delay, bool supportsGetDecodeOutput), so that in
VFSTest, we can add another test param to test both cases?

Am example of using multiple test parameters can be found here:
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/med...

+}
+
+void FakeVideoDecoder::QueueRead() {
+  ++reads_queued_;
+}
+
 void FakeVideoDecoder::HoldNextInit() {
   DCHECK(task_runner_->BelongsToCurrentThread());
   init_cb_.HoldCallback();