Make VideoDecoder use (kAborted, NULL) to signify an aborted decode, instead of (kOk, NULL).

media/filters/video_frame_stream.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/filters/video_frame_stream.h"
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/debug/trace_event.h"
 #include "base/location.h"
@@ skipping 227 matching lines @@
   Decode(DecoderBuffer::CreateEOSBuffer());
 }
 
 void VideoFrameStream::OnFrameReady(int buffer_size,
                                     const VideoDecoder::Status status,
                                     const scoped_refptr<VideoFrame>& frame) {
   DVLOG(2) << __FUNCTION__;
   DCHECK(state_ == STATE_NORMAL || state_ == STATE_FLUSHING_DECODER) << state_;
   DCHECK(!read_cb_.is_null());
   DCHECK(stop_cb_.is_null());
 

[xhwang, 2014/01/03 01:05:58]

DCHECK_EQ(status == VideoDecoder::kOk, frame != NULL);

then we can drop the DCHECK(!frame.get()) in various places in this function.

Since this function (callback) is used by ALL video decoders, this check also
helps you make sure you updated all video decoders.

   TRACE_EVENT_ASYNC_END0("media", "VideoFrameStream::Decode", this);
 
   if (status == VideoDecoder::kDecodeError) {
     DCHECK(!frame.get());
     state_ = STATE_ERROR;
     SatisfyRead(DECODE_ERROR, NULL);
     return;
   }
 
   if (status == VideoDecoder::kDecryptError) {
     DCHECK(!frame.get());
     state_ = STATE_ERROR;
     SatisfyRead(DECRYPT_ERROR, NULL);
     return;
   }
 
+  if (status == VideoDecoder::kAborted) {
+    DCHECK(!frame.get());
+    AbortRead();
+    return;
+  }

[xhwang, 2014/01/03 01:05:58]

VideoDecoder::kAborted can only be a result of a previous VideoDecoder::Reset()
call, which is handled on l.280. This is why we didn't check for (kOk, NULL) in
the original impl. Sorry for not making this obvious :( Feel free to
refactor/clean-up/comment the code to make it cleaner.

Note that kAborted -> !reset_cb_.is_null() but not vice versa. For example, we
could have:
- Decode()
- Decode finished and OnFrameReady posted.
- Reset()
- OnFrameReady(kOk, valid_frame)  // !reset_cb_.is_null()
- Reset callback fired..

+
   // Any successful decode counts!
   if (buffer_size > 0) {
     PipelineStatistics statistics;
     statistics.video_bytes_decoded = buffer_size;
     statistics_cb_.Run(statistics);
   }
 
   // Drop decoding result if Reset() was called during decoding.
   // The resetting process will be handled when the decoder is reset.
   if (!reset_cb_.is_null()) {
@@ skipping 171 matching lines @@
   DCHECK(!stop_cb_.is_null());
 
   state_ = STATE_STOPPED;
   stream_ = NULL;
   decoder_.reset();
   decrypting_demuxer_stream_.reset();
   base::ResetAndReturn(&stop_cb_).Run();
 }
 
 }  // namespace media