Cast: Add GetStats() extensions API.

chrome/renderer/media/cast_session.h

Index: chrome/renderer/media/cast_session.h
diff --git a/chrome/renderer/media/cast_session.h b/chrome/renderer/media/cast_session.h
index 237ea2fa696d4915ad2fd5ef0431068f6b471d0c..f76286c7c810e5ebedd7b8ef442d6651f8718c6e 100644
--- a/chrome/renderer/media/cast_session.h
+++ b/chrome/renderer/media/cast_session.h
@@ -42,6 +42,7 @@ class CastSession : public base::RefCounted<CastSession> {
       FrameInputAvailableCallback;
   typedef base::Callback<void(const std::vector<char>&)> SendPacketCallback;
   typedef base::Callback<void(scoped_ptr<std::string>)> EventLogsCallback;
+  typedef base::Callback<void(scoped_ptr<std::string>)> StatsCallback;
 
   CastSession();
 
@@ -67,6 +68,10 @@ class CastSession : public base::RefCounted<CastSession> {
   // stream since last call and returns result in |callback|.
   void GetEventLogsAndReset(bool is_audio, const EventLogsCallback& callback);
 
+  // Returns stats in a string formatted in JSON for either the audio or video
+  // stream since last call and returns result in |callback|.
+  void GetStatsAndReset(bool is_audio, const StatsCallback& callback);

[Alpha Left Google, 2014/03/03 07:11:39]

Statistics is continuous unlike events. So "AndReset" is not accurate. I think
we should just drop it from this method name.

[imcheng, 2014/03/04 02:06:24]

In the implementation we will probably do a reset though, if we are interested
in real time stats (rather than stats that span the entire session) and we want
to implement this without using a sliding window implementation or similar
(because it will probably cost more memory than we would have liked, especially
with the amount of memory raw events is already using).

+
  private:
   friend class base::RefCounted<CastSession>;
   virtual ~CastSession();