Move RTCI420Frame with minor style changes.

webrtc/api/objc/RTCVideoFrame.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>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface RTCVideoFrame : NSObject
+
+/** Width without rotation applied. */
+@property(nonatomic, readonly) size_t width;
+
+/** Height without rotation applied. */
+@property(nonatomic, readonly) size_t height;
+@property(nonatomic, readonly) size_t chromaWidth;
+@property(nonatomic, readonly) size_t chromaHeight;
+@property(nonatomic, readonly) size_t chromaSize;
+// These can return NULL if the object is not backed by a buffer.
+@property(nonatomic, readonly, nullable) const uint8_t *yPlane;
+@property(nonatomic, readonly, nullable) const uint8_t *uPlane;
+@property(nonatomic, readonly, nullable) const uint8_t *vPlane;
+@property(nonatomic, readonly) int32_t yPitch;
+@property(nonatomic, readonly) int32_t uPitch;
+@property(nonatomic, readonly) int32_t vPitch;
+
+- (instancetype)init NS_UNAVAILABLE;
+
+@end
+
+NS_ASSUME_NONNULL_END