MediaStream audio: Refactor 3 separate "glue" implementations into one.

content/renderer/media/media_stream_source.h

Index: content/renderer/media/media_stream_source.h
diff --git a/content/renderer/media/media_stream_source.h b/content/renderer/media/media_stream_source.h
index 940efcc30a337da6d9e3957943766fda3b594251..f81a68f9e7de646c1f1a3e448a3aabad6eaccd10 100644
--- a/content/renderer/media/media_stream_source.h
+++ b/content/renderer/media/media_stream_source.h
@@ -53,11 +53,6 @@ class CONTENT_EXPORT MediaStreamSource
     stop_callback_.Reset();
   }
 
- protected:
-  // Called when StopSource is called. It allows derived classes to implement
-  // its  own Stop method.
-  virtual void DoStopSource() = 0;
-
   // Sets device information about a source that has been created by a
   // JavaScript call to GetUserMedia. F.E a camera or microphone.
   void SetDeviceInfo(const StreamDeviceInfo& device_info) {
@@ -70,6 +65,11 @@ class CONTENT_EXPORT MediaStreamSource
     stop_callback_ = stop_callback;
   }
 
+ protected:
+  // Called when StopSource is called. It allows derived classes to implement
+  // its  own Stop method.
+  virtual void DoStopSource() = 0;
+
  private:
   StreamDeviceInfo device_info_;
   SourceStoppedCallback stop_callback_;

[o1ka, 2016/03/30 15:00:58]

Looks like we need to add thread checker to this class to make sure all the
access to this data is thread safe. We should not rely on child classes for
this: it's a source of future bugs and also makes it difficult to read the code.
For example, to ensure thread safety of  calls like
[media_stream_audio_source.cc:155], I need to look up all the access to
stop_callback_ in MediaStreamAudioSource - which is not a straightforward things
since it's hidden in MediaStreamSource methods.

[miu, 2016/03/31 04:57:59]

Done.