Add metal view, shaders and renderer.

webrtc/sdk/objc/Framework/Classes/Metal/RTCNV12Renderer.h

Index: webrtc/sdk/objc/Framework/Classes/Metal/RTCNV12Renderer.h
diff --git a/webrtc/sdk/objc/Framework/Classes/Metal/RTCNV12Renderer.h b/webrtc/sdk/objc/Framework/Classes/Metal/RTCNV12Renderer.h
new file mode 100644
index 0000000000000000000000000000000000000000..c02e844729a4375f2216c6a4d1e216595a17cda0
--- /dev/null
+++ b/webrtc/sdk/objc/Framework/Classes/Metal/RTCNV12Renderer.h
@@ -0,0 +1,17 @@
+/*
+ *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#import <Foundation/Foundation.h>
+
+#import "WebRTC/RTCMTLRenderer.h"
+
+/** Implementation of RTCMTLRenderer protocol for rendering native nv12 video frames. */
+@interface RTCNV12Renderer : NSObject <RTCMTLRenderer>
+@end