fix video_decode_accelerator_unittest issue when decode speed is slow

content/common/gpu/media/video_decode_accelerator_unittest.cc

Index: content/common/gpu/media/video_decode_accelerator_unittest.cc
diff --git a/content/common/gpu/media/video_decode_accelerator_unittest.cc b/content/common/gpu/media/video_decode_accelerator_unittest.cc
index 8b89d049b9339115a642f008e93f3796be83eb12..237bc2321ca82d5a538760f54b8eb5672bf3a995 100644
--- a/content/common/gpu/media/video_decode_accelerator_unittest.cc
+++ b/content/common/gpu/media/video_decode_accelerator_unittest.cc
@@ -546,7 +546,13 @@ void GLRenderingVDAClient::NotifyEndOfBitstreamBuffer(
   // VaapiVideoDecodeAccelerator::FinishReset()).
   ++num_done_bitstream_buffers_;
   --outstanding_decodes_;
-  if (decode_calls_per_second_ == 0)
+
+  // flush decoder after all BitstreamBuffer are processed

[Pawel Osciak, 2015/01/20 02:18:00]

Comments should be full English sentences when possible. Please capitalize and
use a dot at the end of the sentence.

+  if (encoded_data_next_pos_to_decode_ == encoded_data_.size() &&
+      outstanding_decodes_ == 0) {

[Pawel Osciak, 2015/01/20 02:18:00]

If the issue is with the decode being slow, shouldn't the proper place for flush
be after we receive the final decoded picture via PictureReady? Decoders may be
returning bitstream buffers before finishing decode for it.

[Owen Lin, 2015/01/20 02:43:00]

The issue happens only when |decode_calls_per_second_| is not 0. In that mode,
we will call DecodeNextFragment() at a constant rate (see l.803 of the base
code). However, when we try to decode the last fragment. The previous bitstream
buffer may still be used by the decoder (This is the slowness). So that
|outstanding_decodes_| is not 0 and we will refuse to flush the decoder (see
l.746 of the base code). That's the bug. 

I think it is correct to move Flush() here since we would like to do the Flush()
after the decoder processes the last bitstream buffer. Besides, it is hard to
tell which one is the "final" picture (I thought the decoder is allowed to keep
some reference frames until we call Flush()).

+    decoder_->Flush();
+    SetState(CS_FLUSHING);
+  } else if (decode_calls_per_second_ == 0)
     DecodeNextFragment();
 }
 
@@ -742,13 +748,9 @@ static bool FragmentHasConfigInfo(const uint8* data, size_t size,
 void GLRenderingVDAClient::DecodeNextFragment() {
   if (decoder_deleted())
     return;
-  if (encoded_data_next_pos_to_decode_ == encoded_data_.size()) {
-    if (outstanding_decodes_ == 0) {
-      decoder_->Flush();
-      SetState(CS_FLUSHING);
-    }
+  if (encoded_data_next_pos_to_decode_ == encoded_data_.size())
     return;
-  }
+
   size_t end_pos;
   std::string next_fragment_bytes;
   if (encoded_data_next_pos_to_decode_ == 0) {