Remove remaining calls to deprecated MessageLoop methods on Mac.

media/cast/sender/h264_vt_encoder_unittest.cc

Index: media/cast/sender/h264_vt_encoder_unittest.cc
diff --git a/media/cast/sender/h264_vt_encoder_unittest.cc b/media/cast/sender/h264_vt_encoder_unittest.cc
index 5a33ffa501a84175041b0b11b747b005885ab56c..efe4adedceda992c1b2aec157395e64bea25160f 100644
--- a/media/cast/sender/h264_vt_encoder_unittest.cc
+++ b/media/cast/sender/h264_vt_encoder_unittest.cc
@@ -320,7 +320,7 @@ TEST_F(H264VideoToolboxEncoderTest, DISABLED_CheckFramesAreDecodable) {
   }
 
   encoder_.reset();
-  message_loop_.RunUntilIdle();
+  base::RunLoop().RunUntilIdle();
 
   EXPECT_EQ(5, checker->count_frames_checked());
 }