VideoToolbox encoder for cast senders.

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 784e8c6a34f2a2d2bfb94c4c0efa18e9bbaaa844..2a801fc06db66e03c21051320d4bf442ef4d9284 100644
--- a/media/cast/sender/video_sender.cc
+++ b/media/cast/sender/video_sender.cc
@@ -16,6 +16,10 @@
 #include "media/cast/sender/external_video_encoder.h"
 #include "media/cast/sender/video_encoder_impl.h"
 
+#if defined(OS_MACOSX)
+#include "media/cast/sender/h264_vt_encoder.h"
+#endif
+
 namespace media {
 namespace cast {
 
@@ -69,6 +73,20 @@ VideoSender::VideoSender(
           << " and max_frame_rate=" << video_config.max_frame_rate;
   DCHECK_GT(max_unacked_frames_, 0);
 
+#if defined(OS_MACOSX)
+  // On Apple platforms, use the hardware H.264 encoder if possible. It is the
+  // only reasonable option for iOS.
+  if (!video_config.use_external_encoder &&
+      video_config.codec == CODEC_VIDEO_H264) {
+    video_encoder_.reset(new H264VideoToolboxEncoder(
+        cast_environment,
+        video_config,
+        base::Bind(&VideoSender::OnEncoderInitialized,
+                   weak_factory_.GetWeakPtr(),
+                   initialization_cb)));
+  }
+#endif  // defined(OS_MACOSX)
+#if !defined(OS_IOS)
   if (video_config.use_external_encoder) {
     video_encoder_.reset(new ExternalVideoEncoder(
         cast_environment,
@@ -77,7 +95,7 @@ VideoSender::VideoSender(
                    weak_factory_.GetWeakPtr(), initialization_cb),
         create_vea_cb,
         create_video_encode_mem_cb));
-  } else {
+  } else if (!video_encoder_) {
     // Software encoder is initialized immediately.
     congestion_control_.reset(
         NewAdaptiveCongestionControl(cast_environment->Clock(),
@@ -88,6 +106,7 @@ VideoSender::VideoSender(
         cast_environment, video_config, max_unacked_frames_));
     cast_initialization_status_ = STATUS_VIDEO_INITIALIZED;
   }
+#endif  // !defined(OS_IOS)
 
   if (cast_initialization_status_ == STATUS_VIDEO_INITIALIZED) {
     cast_environment->PostTask(