Cast: Add GetStats() extensions API.

chrome/renderer/media/cast_session.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_RENDERER_MEDIA_CAST_SESSION_H_
 #define CHROME_RENDERER_MEDIA_CAST_SESSION_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 24 matching lines @@
 // This class represents a Cast session and allows the session to be
 // configured on the main thread. Actual work is forwarded to
 // CastSessionDelegate on the IO thread.
 class CastSession : public base::RefCounted<CastSession> {
  public:
   typedef
   base::Callback<void(const scoped_refptr<media::cast::FrameInput>&)>
       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();
 
   // Start encoding of audio and video using the provided configuration.
   //
   // When Cast sender is started and ready to be used
   // media::cast::FrameInput will be given through the callback. The
   // callback will be made on the main thread.
   void StartAudio(const media::cast::AudioSenderConfig& config,
                   const FrameInputAvailableCallback& callback);
   void StartVideo(const media::cast::VideoSenderConfig& config,
                   const FrameInputAvailableCallback& callback);
   void StartUDP(const net::IPEndPoint& local_endpoint,
                 const net::IPEndPoint& remote_endpoint);
 
   // Creates or destroys event subscriber for the audio or video stream.
   // |is_audio|: true if the event subscriber is for audio. Video otherwise.
   // |enable|: If true, creates an event subscriber. Otherwise destroys
   // existing subscriber and discards logs.
   void ToggleLogging(bool is_audio, bool enable);
 
   // Returns raw event logs in serialized format for either the audio or video
   // 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();
 
   // This member should never be dereferenced on the main thread.
   // CastSessionDelegate lives only on the IO thread. It is always
   // safe to post task on the IO thread to access CastSessionDelegate
   // because it is owned by this object.
   scoped_ptr<CastSessionDelegate> delegate_;
 
   // Proxy to the IO message loop.
   const scoped_refptr<base::MessageLoopProxy> io_message_loop_proxy_;
 
   DISALLOW_COPY_AND_ASSIGN(CastSession);
 };
 
 #endif  // CHROME_RENDERER_MEDIA_CAST_SESSION_H_