media: Introduce Renderer interface and RendererImpl.

media/filters/video_renderer_impl.cc

Index: media/filters/video_renderer_impl.cc
diff --git a/media/filters/video_renderer_impl.cc b/media/filters/video_renderer_impl.cc
index 73419c677dff2952c1718678fc66d079bd262de2..33515420e0abbc8c9e452e85f68ddaee323cafc8 100644
--- a/media/filters/video_renderer_impl.cc
+++ b/media/filters/video_renderer_impl.cc
@@ -11,6 +11,7 @@
 #include "base/location.h"
 #include "base/single_thread_task_runner.h"
 #include "base/threading/platform_thread.h"
+#include "media/base/bind_to_current_loop.h"
 #include "media/base/buffers.h"
 #include "media/base/limits.h"
 #include "media/base/pipeline.h"
@@ -125,7 +126,10 @@ void VideoRendererImpl::Initialize(DemuxerStream* stream,
 
   low_delay_ = low_delay;
 
-  init_cb_ = init_cb;
+  // Always post |init_cb_| because |this| could be destroyed if initialization
+  // failed.

[damienv1, 2014/08/06 16:10:03]

Could you please give me a callstack / sequence of events where this is an issue
?
This seems to me sth that should be handled by the owner of VideoRendererImpl
not by VideoRendererImpl itself.

[xhwang, 2014/08/07 05:46:49]

See:
https://codereview.chromium.org/418143005/diff/140001/media/filters/renderer_...

Basically in media code the callee should post instead of relying on the caller
to post. Maybe I should just make it an explicitly PostTask.

+  init_cb_ = BindToCurrentLoop(init_cb);
+
   statistics_cb_ = statistics_cb;
   max_time_cb_ = max_time_cb;
   buffering_state_cb_ = buffering_state_cb;
@@ -283,6 +287,7 @@ void VideoRendererImpl::DropNextReadyFrame_Locked() {
 
 void VideoRendererImpl::FrameReady(VideoFrameStream::Status status,
                                    const scoped_refptr<VideoFrame>& frame) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
   base::AutoLock auto_lock(lock_);
   DCHECK_NE(state_, kUninitialized);
   DCHECK_NE(state_, kFlushed);
@@ -296,7 +301,7 @@ void VideoRendererImpl::FrameReady(VideoFrameStream::Status status,
     PipelineStatus error = PIPELINE_ERROR_DECODE;
     if (status == VideoFrameStream::DECRYPT_ERROR)
       error = PIPELINE_ERROR_DECRYPT;
-    error_cb_.Run(error);
+    task_runner_->PostTask(FROM_HERE, base::Bind(error_cb_, error));
     return;
   }