Avoid double task trampoline for Pipeline state transitions.

media/mojo/services/mojo_renderer_impl.cc

 // Copyright 2014 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/mojo/services/mojo_renderer_impl.h"
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/location.h"
 #include "base/single_thread_task_runner.h"
@@ skipping 38 matching lines @@
   // current thread so we can use it. The MojoRendererImpl object
   // is constructed on another thread so we can't do it in the
   // constructor and must pass a message pipe around since
   // InterfacePtr's are tied to the message loop they were created on.
   remote_media_renderer_.Bind(remote_media_renderer_pipe_.Pass());
   DCHECK(remote_media_renderer_);
   remote_media_renderer_.set_client(this);
 
   demuxer_stream_provider_ = demuxer_stream_provider;
   // |init_cb| can be called on other thread.
-  init_cb_ = init_cb;
+  init_cb_ = BindToCurrentLoop(init_cb);
   ended_cb_ = ended_cb;
   error_cb_ = error_cb;
   buffering_state_cb_ = buffering_state_cb;
 
   // Create audio and video mojo::DemuxerStream and bind its lifetime to the
   // pipe.
   DemuxerStream* const audio =
       demuxer_stream_provider_->GetStream(DemuxerStream::AUDIO);
   DemuxerStream* const video =
       demuxer_stream_provider_->GetStream(DemuxerStream::VIDEO);
 
   mojo::DemuxerStreamPtr audio_stream;
   if (audio) {
     mojo::BindToProxy(new MojoDemuxerStreamImpl(audio), &audio_stream)
         ->DidConnect();
   }
 
   mojo::DemuxerStreamPtr video_stream;
   if (video) {
     mojo::BindToProxy(new MojoDemuxerStreamImpl(video), &video_stream)
         ->DidConnect();
   }
 
   remote_media_renderer_->Initialize(
       audio_stream.Pass(),
       video_stream.Pass(),
       BindToCurrentLoop(base::Bind(&MojoRendererImpl::OnInitialized,
                                    weak_factory_.GetWeakPtr())));

[xhwang, 2015/01/16 23:09:07]

ditto: we have three posts here:
1, BindToCurrentLoop on l.59.
2, remote_media_renderer_->Initialize() is a mojo call, which is async.
3, BindToCurrentLoop on l.86.

[DaleCurtis, 2015/01/20 21:37:44]

Done.

 }
 
 void MojoRendererImpl::SetCdm(CdmContext* cdm_context,
                               const CdmAttachedCB& cdm_attached_cb) {
   DVLOG(1) << __FUNCTION__;
   DCHECK(task_runner_->BelongsToCurrentThread());
   NOTIMPLEMENTED();
   cdm_attached_cb.Run(false);
 }
 
@@ skipping 92 matching lines @@
 
 void MojoRendererImpl::OnError() {
   DVLOG(1) << __FUNCTION__;
 
   if (!task_runner_->BelongsToCurrentThread()) {
     task_runner_->PostTask(
         FROM_HERE,
         base::Bind(&MojoRendererImpl::OnError, weak_factory_.GetWeakPtr()));
     return;
   }
 

[DaleCurtis, 2015/01/20 21:37:44]

Hmm looks like this code should run init_cb_ on error?

[xhwang, 2015/01/20 23:00:38]

Looks like we are relying on OnInitialized() to fire |init_cb|. So if we have
error happened during initialization, we should get an OnError() first, then get
an OnInitialized().

   // TODO(tim): Should we plumb error code from remote renderer?
   // http://crbug.com/410451.
   if (init_cb_.is_null())  // We have initialized already.
     error_cb_.Run(PIPELINE_ERROR_DECODE);
   else
     error_cb_.Run(PIPELINE_ERROR_COULD_NOT_RENDER);
 }
 
 void MojoRendererImpl::OnInitialized() {
   DVLOG(1) << __FUNCTION__;
   DCHECK(task_runner_->BelongsToCurrentThread());
   DCHECK(!init_cb_.is_null());
 
   base::ResetAndReturn(&init_cb_).Run();
 }
 
 }  // namespace media