Reland of Add unit tests for RTCMTLVideoView.

webrtc/sdk/objc/Framework/Classes/Metal/RTCMTLNV12Renderer.h

 /*
  *  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 <MetalKit/MTKView.h>
 
 #import "WebRTC/RTCVideoFrame.h"
 
 /**
  * Protocol defining ability to render RTCVideoFrame in Metal enabled views.
  */
 @protocol RTCMTLRenderer <NSObject>
 
 /**
  * Method to be implemented to perform actual rendering of the provided frame.
  *
  * @param frame The frame to be rendered.
  */
 - (void)drawFrame:(RTCVideoFrame *)frame;
+
+/**
+ * Sets the provided view as rendering destination if possible.
+ *
+ * If not possible method returns NO and callers of the method are responisble for performing
+ * cleanups.
+ */
+- (BOOL)addRenderingDestination:(__kindof UIView *)view;
+
 @end
 
 /**
  * Implementation of RTCMTLRenderer protocol for rendering native nv12 video frames.
  */
 @interface RTCMTLNV12Renderer : NSObject <RTCMTLRenderer>
 
-/**
- * Sets the provided view as rendering destination if possible.
- *
- * If not possible method returns NO and callers of the method are responisble for performing
- * cleanups.
- */
-- (BOOL)addRenderingDestination:(__kindof MTKView *)view;
 @end