Add metal view, shaders and renderer.

webrtc/sdk/objc/Framework/Classes/Metal/RTCMTLVideoView.m

+/*
+ *  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 "WebRTC/RTCMTLVideoView.h"
+
+#import <Metal/Metal.h>
+#import <MetalKit/MetalKit.h>
+
+#import "RTCNV12Renderer.h"
+
+@interface RTCMTLVideoView ()
+@property (nonatomic) id<RTCMTLRenderer> renderer;
+@property (nonatomic, strong) __kindof UIView *metalView;
+@end
+
+@implementation RTCMTLVideoView {
+  id<RTCMTLRenderer> _renderer;
+}
+
+@synthesize renderer = _renderer;
+@synthesize metalView = _metalView;
+
+- (instancetype)initWithFrame:(CGRect)frameRect {
+  self = [super initWithFrame:frameRect];
+#if defined(__OBJC__) && COREVIDEO_SUPPORTS_METAL
+  if (self) {
+    _metalView = [[MTKView alloc] initWithFrame:frameRect];
+    [self addSubview:_metalView];
+    _metalView.translatesAutoresizingMaskIntoConstraints = NO;
+    UILayoutGuide *margins = self.layoutMarginsGuide;
+    [_metalView.topAnchor constraintEqualToAnchor:margins.topAnchor].active = YES;
+    [_metalView.bottomAnchor constraintEqualToAnchor:margins.bottomAnchor].active = YES;
+    [_metalView.leftAnchor constraintEqualToAnchor:margins.leftAnchor].active = YES;
+    [_metalView.rightAnchor constraintEqualToAnchor:margins.rightAnchor].active = YES;
+
+     _renderer = [[RTCNV12Renderer alloc] initWithView:_metalView];

[Chuck, 2017/02/15 14:54:05]

Is this indented 1 too many spaces?

+  }
+#endif
+  return self;
+}
+
+- (BOOL)setupRenderer {
+  return [_renderer setup];
+}
+
+@end