Add Cast PLI support on sender side.

media/cast/sender/frame_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.
 //
 // This is the base class for an object that send frames to a receiver.
 // TODO(hclam): Refactor such that there is no separate AudioSender vs.
 // VideoSender, and the functionality of both is rolled into this class.
 
 #ifndef MEDIA_CAST_SENDER_FRAME_SENDER_H_
 #define MEDIA_CAST_SENDER_FRAME_SENDER_H_
@@ skipping 74 matching lines @@
   // speculatively re-send certain packets of an unacked frame to kick-start
   // re-transmission.  This is a last resort tactic to prevent the session from
   // getting stuck after a long outage.
   void ScheduleNextResendCheck();
   void ResendCheck();
   void ResendForKickstart();
 
   // Protected for testability.
   void OnReceivedCastFeedback(const RtcpCastMessage& cast_feedback);
 
+  // Called when receiving a Pli message from the receiver.
+  void OnReceivedPli();
+
   // Returns true if too many frames would be in-flight by encoding and sending
   // the next frame having the given |frame_duration|.
   bool ShouldDropNextFrame(base::TimeDelta frame_duration) const;
 
   // Record or retrieve a recent history of each frame's timestamps.
   // Warning: If a frame ID too far in the past is requested, the getters will
   // silently succeed but return incorrect values.  Be sure to respect
   // media::cast::kMaxUnackedFrames.
   void RecordLatestFrameTimestamps(uint32_t frame_id,
                                    base::TimeTicks reference_time,
@@ skipping 54 matching lines @@
   // case, VideoSender will trigger a re-send of the next frame.
   int duplicate_ack_counter_;
 
   // This object controls how we change the bitrate to make sure the
   // buffer doesn't overflow.
   scoped_ptr<CongestionControl> congestion_control_;
 
   // The most recently measured round trip time.
   base::TimeDelta current_round_trip_time_;
 
+  // This flag is set true when received a Pli message from the receiver. It is
+  // cleared after FrameSender receiving an encoded key frame.
+  bool picture_lost_at_receiver_;

[Irfan, 2016/02/29 16:01:23]

may be: This flag is set to true when a PLI message is received. It is cleared
once the FrameSender scheduled an encoded key frame to be sent.

[xjz, 2016/02/29 19:48:58]

Done.

+
  private:
   // Returns the maximum media duration currently allowed in-flight.  This
   // fluctuates in response to the currently-measured network latency.
   base::TimeDelta GetAllowedInFlightMediaDuration() const;
 
   // RTP timestamp increment representing one second.
   const int rtp_timebase_;
 
   const bool is_audio_;
 
   // Ring buffers to keep track of recent frame timestamps (both in terms of
   // local reference time and RTP media time).  These should only be accessed
   // through the Record/GetXXX() methods.
   base::TimeTicks frame_reference_times_[256];
   RtpTimeTicks frame_rtp_timestamps_[256];
 
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<FrameSender> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(FrameSender);
 };
 
 }  // namespace cast
 }  // namespace media
 
 #endif  // MEDIA_CAST_SENDER_FRAME_SENDER_H_