Reland of Injectable Obj-C video codecs

webrtc/sdk/objc/Framework/Headers/WebRTC/RTCVideoCodecFactory.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 <WebRTC/RTCMacros.h>
+#import <WebRTC/RTCVideoCodec.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+/** RTCVideoEncoderFactory is an Objective-C version of cricket::WebRtcVideoEncoderFactory. */
+RTC_EXPORT
+@protocol RTCVideoEncoderFactory <NSObject>
+
+- (id<RTCVideoEncoder>)createEncoder:(RTCVideoCodecInfo *)info;
+- (NSArray<RTCVideoCodecInfo *> *)supportedCodecs;
+
+@end
+
+/** RTCVideoDecoderFactory is an Objective-C version of cricket::WebRtcVideoDecoderFactory. */
+RTC_EXPORT
+@protocol RTCVideoDecoderFactory <NSObject>
+
+- (id<RTCVideoDecoder>)createDecoder:(RTCVideoCodecInfo *)info;
+- (NSArray<RTCVideoCodecInfo *> *)supportedCodecs;
+
+@end
+
+NS_ASSUME_NONNULL_END