Add metal view, shaders and renderer.

webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMTLVideoView.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/MetalKit.h>
+#import "WebRTC/RTCVideoRenderer.h"
+
+NS_ASSUME_NONNULL_BEGIN
+RTC_EXPORT
+
+/**
+ * RTCMTLVideoView is thin wrapper around MTKView.
+ *
+ * It has id<RTCVideoRenderer> property that renders video frames in the view's
+ * bounds using Metal.
+ */
+@interface RTCMTLVideoView : MTKView

[tkchin_webrtc, 2017/02/10 23:32:10]

I think it is better to subclass UIView here instead.

[daniela-webrtc, 2017/02/13 12:32:07]

You are right. I'm already working on a follow up CL to change that. Is it OK to
keep that in the separate on as it's little bit more than one liner change?

[tkchin_webrtc, 2017/02/14 00:23:56]

I would prefer that headers that are checked into this directory are already
100% ready to go, since this API is public and we want to maintain it
gracefully.
If it's still in development, can we put this file elsewhere temporarily?

+
+/**
+ * Renderer class that can render RTCVideoTrack.
+ */
+@property(nonatomic, readonly) id<RTCVideoRenderer> renderer;
+
+/**
+ * Sets up the renderer.
+ *
+ * If the method returns NO it signifies the renderer is unable to perform proper setup and
+ * it's responsibility of the caller to perform all necessary clean up after this point.
+ * Unexpected behavior can happen if the cleanup doesn't happen.
+ */
+- (BOOL)setupRenderer;
+
+#pragma mark - Unavailable

[tkchin_webrtc, 2017/02/10 23:32:10]

nit: don't need this pragma

+- (instancetype)init NS_UNAVAILABLE;
++ (instancetype) new NS_UNAVAILABLE;

[tkchin_webrtc, 2017/02/10 23:32:10]

nit: remove space
also, ooc why is new explicitly forbidden?

[daniela-webrtc, 2017/02/13 12:32:07]

Initially it was there because I did the renderer alloc in a non-designated
initializer. I guess I forgot to remove this when I moved the allocation in a
designated initializer. Prohibiting the init/new is no longer needed.

+@end
+NS_ASSUME_NONNULL_END