Move RTCAVFoundationCapturer to webrtc/api/objc.

webrtc/api/objc/RTCAVFoundationVideoSource.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 "RTCVideoSource.h"
+
+@class AVCaptureSession;
+@class RTCMediaConstraints;
+@class RTCPeerConnectionFactory;
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ * RTCAVFoundationVideoSource is a video source that uses
+ * webrtc::AVFoundationVideoCapturer. We do not currently provide a wrapper for
+ * that capturer because cricket::VideoCapturer is not ref counted and we cannot
+ * guarantee its lifetime. Instead, we expose its properties through the ref
+ * counted video source interface.
+ */
+@interface RTCAVFoundationVideoSource : RTCVideoSource
+
+- (instancetype)initWithFactory:(RTCPeerConnectionFactory *)factory
+                    constraints:(RTCMediaConstraints *)constraints;
+
+/** Switches the camera being used (either front or back). */
+@property(nonatomic, assign) BOOL useBackCamera;
+
+/** Returns the active capture session. */
+@property(nonatomic, readonly) AVCaptureSession *captureSession;
+
+@end
+
+
+NS_ASSUME_NONNULL_END