[cast] Stub out call to VideoEncoderImpl::IsSupported on iOS.

media/cast/sender/video_encoder.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/cast/sender/video_encoder.h"
 
 #include "media/cast/sender/external_video_encoder.h"
 #include "media/cast/sender/video_encoder_impl.h"
 
 #if defined(OS_MACOSX)
@@ skipping 16 matching lines @@
   if (!video_config.use_external_encoder &&
       H264VideoToolboxEncoder::IsSupported(video_config)) {
     return scoped_ptr<VideoEncoder>(
         new SizeAdaptableH264VideoToolboxVideoEncoder(
             cast_environment,
             video_config,
             status_change_cb));
   }
 #endif  // defined(OS_MACOSX)
 
+#if !defined(OS_IOS)
   // If the system provides a hardware-accelerated encoder, use it.
-#if !defined(OS_IOS)
   if (ExternalVideoEncoder::IsSupported(video_config)) {
     return scoped_ptr<VideoEncoder>(new SizeAdaptableExternalVideoEncoder(
         cast_environment,
         video_config,
         status_change_cb,
         create_vea_cb,
         create_video_encode_memory_cb));
   }
-#endif  // !defined(OS_IOS)
 
   // Attempt to use the software encoder implementation.
   if (VideoEncoderImpl::IsSupported(video_config)) {
     return scoped_ptr<VideoEncoder>(new VideoEncoderImpl(
         cast_environment,
         video_config,
         status_change_cb));
   }
+#endif  // !defined(OS_IOS)
 
   // No encoder implementation will suffice.
   return nullptr;
 }
 
 scoped_ptr<VideoFrameFactory> VideoEncoder::CreateVideoFrameFactory() {
   return nullptr;
 }
 
 void VideoEncoder::EmitFrames() {
 }
 
 }  // namespace cast
 }  // namespace media