cast: Support for low-latency interactive mode

media/cast/sender/video_sender.h

Index: media/cast/sender/video_sender.h
diff --git a/media/cast/sender/video_sender.h b/media/cast/sender/video_sender.h
index ab31e7b9b3562185474864c02c47a591fff15780..8869454f478e7f29e5d44ae53b1df0835b52735d 100644
--- a/media/cast/sender/video_sender.h
+++ b/media/cast/sender/video_sender.h
@@ -98,6 +98,11 @@ class VideoSender : public FrameSender,
 
   PlayoutDelayChangeCB playout_delay_change_cb_;
 
+  // Indicates we are operating in a mode where the target playout latency is
+  // 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.