Adding a Metal RGB renderer.

The new RTCMTLRGBRenderer dynamically handles both the kCVPixelFormatType_32BGRA
and the kCVPixelFormatType_32ARGB pixel formats.

Change-Id: I935532f762eff74c4b84fea9b855191f4c321fb7
Bug: webrtc:9200
Reviewed-on: https://webrtc-review.googlesource.com/72482
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Anders Carlsson <andersc@webrtc.org>
Commit-Queue: Peter Hanspers <peterhanspers@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23100}
diff --git a/sdk/objc/Framework/Classes/Metal/RTCMTLRGBRenderer.h b/sdk/objc/Framework/Classes/Metal/RTCMTLRGBRenderer.h
new file mode 100644
index 0000000..de27055
--- /dev/null
+++ b/sdk/objc/Framework/Classes/Metal/RTCMTLRGBRenderer.h
@@ -0,0 +1,21 @@
+/*
+ *  Copyright 2018 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 "RTCMTLRenderer.h"
+
+/** @abstract RGB/BGR renderer.
+ *  @discussion This renderer handles both kCVPixelFormatType_32BGRA and kCVPixelFormatType_32ARGB.
+ */
+NS_AVAILABLE(10_11, 9_0)
+@interface RTCMTLRGBRenderer : RTCMTLRenderer
+
+@end