Add Cast PLI support on sender side.

media/cast/sender/video_sender.h

 // Copyright 2014 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 MEDIA_CAST_SENDER_VIDEO_SENDER_H_
 #define MEDIA_CAST_SENDER_VIDEO_SENDER_H_
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
@@ skipping 86 matching lines @@
   // low for best user experience. When operating in low latency mode, we
   // prefer dropping frames over increasing target playout time.
   bool low_latency_mode_;
 
   // The video encoder's performance metrics as of the last call to
   // OnEncodedVideoFrame().  See header file comments for SenderEncodedFrame for
   // an explanation of these values.
   double last_reported_deadline_utilization_;
   double last_reported_lossy_utilization_;
 
+  base::TimeTicks last_encoded_key_frame_;

[miu, 2016/02/26 23:36:07]

Need comment.  What it is, and why we're tracking it.

[xjz, 2016/02/27 05:53:32]

Done.

+
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<VideoSender> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(VideoSender);
 };
 
 }  // namespace cast
 }  // namespace media
 
 #endif  // MEDIA_CAST_SENDER_VIDEO_SENDER_H_