Add Cast PLI support on sender side.

media/cast/sender/video_sender.cc

Index: media/cast/sender/video_sender.cc
diff --git a/media/cast/sender/video_sender.cc b/media/cast/sender/video_sender.cc
index 1c39ecbc786c8646b1d92a2262857839cf8348bf..b05e8f82049837fd276d8665f8ddf2e9d27d44e4 100644
--- a/media/cast/sender/video_sender.cc
+++ b/media/cast/sender/video_sender.cc
@@ -41,6 +41,10 @@ const int kConstantTimeMs = 75;
 // available to handle the occasional more-complex frames).
 const int kTargetUtilizationPercentage = 75;
 
+// This is the minimum duration in milliseconds that the sender will response

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

will respond

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

Done.

+// to muliple Pli messages.
+const int kMinPliResolveIntervalMs = 500;

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

may be: kMinPliResponseIntervaleMs

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

Done.

+
 // Extract capture begin/end timestamps from |video_frame|'s metadata and log
 // it.
 void LogVideoCaptureTimestamps(CastEnvironment* cast_environment,
@@ -134,11 +138,11 @@ VideoSender::VideoSender(
   transport_config.aes_iv_mask = video_config.aes_iv_mask;
 
   transport_sender->InitializeVideo(
-      transport_config,
-      base::Bind(&VideoSender::OnReceivedCastFeedback,
-                 weak_factory_.GetWeakPtr()),
+      transport_config, base::Bind(&VideoSender::OnReceivedCastFeedback,
+                                   weak_factory_.GetWeakPtr()),
       base::Bind(&VideoSender::OnMeasuredRoundTripTime,
-                 weak_factory_.GetWeakPtr()));
+                 weak_factory_.GetWeakPtr()),
+      base::Bind(&VideoSender::OnReceivedPli, weak_factory_.GetWeakPtr()));
 }
 
 VideoSender::~VideoSender() {
@@ -192,6 +196,18 @@ void VideoSender::InsertRawVideoFrame(
     return;
   }
 
+  // Request a key frame when received a Pli message, and it has been passed
+  // more than |kMinPliResolveIntervalMs| milliseconds from the last key frame
+  // request sent to encoder.
+  if (picture_lost_at_receiver_) {
+    if (last_attempt_to_resolve_picture_loss_.is_null() ||
+        ((reference_time - last_attempt_to_resolve_picture_loss_)
+             .InMilliseconds() > kMinPliResolveIntervalMs)) {
+      video_encoder_->GenerateKeyFrame();
+      last_attempt_to_resolve_picture_loss_ = reference_time;
+    }
+  }
+
   // Two video frames are needed to compute the exact media duration added by
   // the next frame.  If there are no frames in the encoder, compute a guess
   // based on the configured |max_frame_rate_|.  Any error introduced by this