Allow media track switching.

media/renderers/default_renderer_factory.cc

Index: media/renderers/default_renderer_factory.cc
diff --git a/media/renderers/default_renderer_factory.cc b/media/renderers/default_renderer_factory.cc
index 5ccfb7b87d51c0c4fb18ad3314507affe7050ae5..8a6f375dcabf2278c9565ea8bdc8923073149fbb 100644
--- a/media/renderers/default_renderer_factory.cc
+++ b/media/renderers/default_renderer_factory.cc
@@ -104,7 +104,11 @@ std::unique_ptr<Renderer> DefaultRendererFactory::CreateRenderer(
 
   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())
@@ -112,7 +116,11 @@ std::unique_ptr<Renderer> DefaultRendererFactory::CreateRenderer(
 
   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>(