iOS: Add interface for injecting custom shaders

webrtc/sdk/objc/Framework/Headers/WebRTC/RTCEAGLVideoView.h

 /*
  *  Copyright 2015 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 <UIKit/UIKit.h>
 
 #import <WebRTC/RTCMacros.h>
 #import <WebRTC/RTCVideoRenderer.h>
+#import <WebRTC/RTCVideoViewShaderDelegate.h>
 
 NS_ASSUME_NONNULL_BEGIN
 
 @class RTCEAGLVideoView;
 RTC_EXPORT
 @protocol RTCEAGLVideoViewDelegate
 
 - (void)videoView:(RTCEAGLVideoView *)videoView didChangeVideoSize:(CGSize)size;
 
 @end
 
 /**
  * RTCEAGLVideoView is an RTCVideoRenderer which renders video frames in its
- * bounds using OpenGLES 2.0.
+ * bounds using OpenGLES 2.0 or OpenGLES 3.0.
  */
 RTC_EXPORT
 @interface RTCEAGLVideoView : UIView <RTCVideoRenderer>
 
 @property(nonatomic, weak) id<RTCEAGLVideoViewDelegate> delegate;
 
+- (instancetype)initWithFrame:(CGRect)frame

[sakal, 2017/05/11 10:45:47]

Should we mark the default initializer as unavailable?

[magjed_webrtc, 2017/05/11 12:38:06]

The default initializers are still available. That's where we create the
DefaultShader and call these initializers.

+               shaderDelegate:(id<RTCVideoViewShaderDelegate>)shaderDelegate
+    NS_DESIGNATED_INITIALIZER;
+
+- (instancetype)initWithCoder:(NSCoder *)aDecoder
+               shaderDelegate:(id<RTCVideoViewShaderDelegate>)shaderDelegate
+    NS_DESIGNATED_INITIALIZER;
+
 @end
 
 NS_ASSUME_NONNULL_END