Cast: Use fixed bitrate and set it once for hardware encoder

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 09fac8d47821482fdb2a9a6d971c65718b8de1d4..bf96e7bb92ea955f9c6b4c4d6ad1d026c1176dc7 100644
--- a/media/cast/sender/video_sender.h
+++ b/media/cast/sender/video_sender.h
@@ -92,6 +92,11 @@ class VideoSender : public FrameSender,
   // new frames shall halt.
   const int max_unacked_frames_;
 
+  // If this value is non zero then a fixed value is used for bitrate.
+  // If external video encoder is used then bitrate will be fixed to
+  // (min_bitrate + max_bitrate) / 2.
+  const size_t fixed_bitrate_;
+
   // Encodes media::VideoFrame images into EncodedFrames.  Per configuration,
   // this will point to either the internal software-based encoder or a proxy to
   // a hardware-based encoder.