Allow media track switching.

media/renderers/default_renderer_factory.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/renderers/default_renderer_factory.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
@@ skipping 86 matching lines @@
 std::unique_ptr<Renderer> DefaultRendererFactory::CreateRenderer(
     const scoped_refptr<base::SingleThreadTaskRunner>& media_task_runner,
     const scoped_refptr<base::TaskRunner>& worker_task_runner,
     AudioRendererSink* audio_renderer_sink,
     VideoRendererSink* video_renderer_sink,
     const RequestSurfaceCB& request_surface_cb) {
   DCHECK(audio_renderer_sink);
 
   std::unique_ptr<AudioRenderer> audio_renderer(new AudioRendererImpl(
       media_task_runner, audio_renderer_sink,
-      CreateAudioDecoders(media_task_runner), media_log_));
+      // Unretained is safe, since RendererFactory is owned by WMPI, which also
+      // owns RendererImpl and thus AudioRendererImpl.

[xhwang, 2017/03/22 22:31:12]

Checked WMPI, |renderer_factory_| will be destroyed before the
|pipeline_controller_| during destruction, so this comment isn't sufficient. You
can probably say RendererImpl and thus AudioRendererImpl will be destroyed
explicit in WMPI's dtor (pipeline_controller_.Stop()), which happens before
|renderer_factory_| is destructed.

[servolk, 2017/03/23 17:08:10]

Done.

+      base::Bind(&DefaultRendererFactory::CreateAudioDecoders,
+                 base::Unretained(this), media_task_runner),
+      media_log_));
 
   GpuVideoAcceleratorFactories* gpu_factories = nullptr;
   if (!get_gpu_factories_cb_.is_null())
     gpu_factories = get_gpu_factories_cb_.Run();
 
   std::unique_ptr<VideoRenderer> video_renderer(new VideoRendererImpl(
       media_task_runner, worker_task_runner, video_renderer_sink,
-      CreateVideoDecoders(media_task_runner, request_surface_cb, gpu_factories),
+      // Unretained is safe, since RendererFactory is owned by WMPI, which also
+      // owns RendererImpl and thus VideoRendererImpl.
+      base::Bind(&DefaultRendererFactory::CreateVideoDecoders,
+                 base::Unretained(this), media_task_runner, request_surface_cb,
+                 gpu_factories),
       true, gpu_factories, media_log_));
 
   return base::MakeUnique<RendererImpl>(
       media_task_runner, std::move(audio_renderer), std::move(video_renderer));
 }
 
 }  // namespace media