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..7c451564d6f00bc514153e55c9d700ba29f81c5e 100644
--- a/content/renderer/media/media_stream_source.h
+++ b/content/renderer/media/media_stream_source.h
@@ -9,6 +9,7 @@
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "base/macros.h"
+#include "base/threading/thread_checker.h"
 #include "content/common/content_export.h"
 #include "content/common/media/media_stream_options.h"
 #include "third_party/WebKit/public/platform/WebMediaStreamSource.h"
@@ -43,37 +44,40 @@ class CONTENT_EXPORT MediaStreamSource
     return device_info_;
   }
 
-  // Stops the source (by calling DoStopSource()). This sets the
-  // WebMediaStreamSource::readyState to ended, triggers the |stop_callback_|
-  // if set. All pointers to this object are invalid after calling this.
+  // Stops the source (by calling DoStopSource()). This runs the
+  // |stop_callback_| (if set), and then sets the
+  // WebMediaStreamSource::readyState to ended.
   void StopSource();
 
-  void ResetSourceStoppedCallback() {
-    DCHECK(!stop_callback_.is_null());
-    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) {
-    device_info_ = device_info;
-  }
+  void SetDeviceInfo(const StreamDeviceInfo& device_info);
 
   // Sets a callback that will be triggered when StopSource is called.
-  void SetStopCallback(const SourceStoppedCallback& stop_callback) {
-    DCHECK(stop_callback_.is_null());
-    stop_callback_ = stop_callback;
-  }
+  void SetStopCallback(const SourceStoppedCallback& stop_callback);
+
+  // Clears the previously-set SourceStoppedCallback so that it will not be run
+  // in the future.
+  void ResetSourceStoppedCallback();
+
+ protected:
+  // Called when StopSource is called. It allows derived classes to implement
+  // its own Stop method.
+  virtual void DoStopSource() = 0;
 
  private:
+  // Called by both StopSource() and the destructor to ensure the
+  // |stop_callback_| has been run and the blink::WebMediaStreamSource's ready
+  // state has been set to "ended."
+  void RunStopCallbackAndEndStream();
+
   StreamDeviceInfo device_info_;
   SourceStoppedCallback stop_callback_;
 
+  // In debug builds, check that all methods are being called on the main
+  // thread.
+  base::ThreadChecker thread_checker_;
+
   DISALLOW_COPY_AND_ASSIGN(MediaStreamSource);
 };