[Cast] Clean-up: Move max_unacked_frames into CongestionControl.

media/cast/sender/video_encoder_impl_unittest.cc

Index: media/cast/sender/video_encoder_impl_unittest.cc
diff --git a/media/cast/sender/video_encoder_impl_unittest.cc b/media/cast/sender/video_encoder_impl_unittest.cc
index adacdd00ab7846111ca2907840eef11554285e77..7c0047ff7f0dd68a28b688d9f1d1074891a52afc 100644
--- a/media/cast/sender/video_encoder_impl_unittest.cc
+++ b/media/cast/sender/video_encoder_impl_unittest.cc
@@ -108,9 +108,8 @@ class VideoEncoderImplTest : public ::testing::Test {
   void CreateEncoder() {
     test_video_encoder_callback_ = new TestVideoEncoderCallback(
         video_config_.max_number_of_video_buffers_used != 1);
-    video_encoder_.reset(new VideoEncoderImpl(
-        cast_environment_, video_config_,
-        0 /* useless arg to be removed in later change */));
+    video_encoder_.reset(
+        new VideoEncoderImpl(cast_environment_, video_config_));
   }
 
   void AdvanceClockAndVideoFrameTimestamp() {