Obj-C SDK Cleanup

This CL separates the files under sdk/objc into logical directories, replacing
the previous file layout under Framework/.

A long term goal is to have some system set up to generate the files under
sdk/objc/api (the PeerConnection API wrappers) from the C++ code. In the shorter
term the goal is to abstract out shared concepts from these classes in order to
make them as uniform as possible.

The separation into base/, components/, and helpers/ are to differentiate between
the base layer's common protocols, various utilities and the actual platform
specific components.

The old directory layout that resembled a framework's internal layout is not
necessary, since it is generated by the framework target when building it.

Bug: webrtc:9627
Change-Id: Ib084fd83f050ae980649ca99e841f4fb0580bd8f
Reviewed-on: https://webrtc-review.googlesource.com/94142
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Reviewed-by: Henrik Andreassson <henrika@webrtc.org>
Commit-Queue: Anders Carlsson <andersc@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24493}
diff --git a/sdk/objc/Framework/Headers/WebRTC/RTCRtpReceiver.h b/sdk/objc/Framework/Headers/WebRTC/RTCRtpReceiver.h
index 6156db9..ff61f82 100644
--- a/sdk/objc/Framework/Headers/WebRTC/RTCRtpReceiver.h
+++ b/sdk/objc/Framework/Headers/WebRTC/RTCRtpReceiver.h
@@ -8,75 +8,4 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#import <Foundation/Foundation.h>
-
-#import <WebRTC/RTCMacros.h>
-#import <WebRTC/RTCMediaStreamTrack.h>
-#import <WebRTC/RTCRtpParameters.h>
-
-NS_ASSUME_NONNULL_BEGIN
-
-/** Represents the media type of the RtpReceiver. */
-typedef NS_ENUM(NSInteger, RTCRtpMediaType) {
-  RTCRtpMediaTypeAudio,
-  RTCRtpMediaTypeVideo,
-  RTCRtpMediaTypeData,
-};
-
-@class RTCRtpReceiver;
-
-RTC_EXPORT
-@protocol RTCRtpReceiverDelegate <NSObject>
-
-/** Called when the first RTP packet is received.
- *
- *  Note: Currently if there are multiple RtpReceivers of the same media type,
- *  they will all call OnFirstPacketReceived at once.
- *
- *  For example, if we create three audio receivers, A/B/C, they will listen to
- *  the same signal from the underneath network layer. Whenever the first audio packet
- *  is received, the underneath signal will be fired. All the receivers A/B/C will be
- *  notified and the callback of the receiver's delegate will be called.
- *
- *  The process is the same for video receivers.
- */
-- (void)rtpReceiver:(RTCRtpReceiver *)rtpReceiver
-    didReceiveFirstPacketForMediaType:(RTCRtpMediaType)mediaType;
-
-@end
-
-RTC_EXPORT
-@protocol RTCRtpReceiver <NSObject>
-
-/** A unique identifier for this receiver. */
-@property(nonatomic, readonly) NSString *receiverId;
-
-/** The currently active RTCRtpParameters, as defined in
- *  https://www.w3.org/TR/webrtc/#idl-def-RTCRtpParameters.
- *
- *  The WebRTC specification only defines RTCRtpParameters in terms of senders,
- *  but this API also applies them to receivers, similar to ORTC:
- *  http://ortc.org/wp-content/uploads/2016/03/ortc.html#rtcrtpparameters*.
- */
-@property(nonatomic, readonly) RTCRtpParameters *parameters;
-
-/** The RTCMediaStreamTrack associated with the receiver.
- *  Note: reading this property returns a new instance of
- *  RTCMediaStreamTrack. Use isEqual: instead of == to compare
- *  RTCMediaStreamTrack instances.
- */
-@property(nonatomic, readonly, nullable) RTCMediaStreamTrack *track;
-
-/** The delegate for this RtpReceiver. */
-@property(nonatomic, weak) id<RTCRtpReceiverDelegate> delegate;
-
-@end
-
-RTC_EXPORT
-@interface RTCRtpReceiver : NSObject <RTCRtpReceiver>
-
-- (instancetype)init NS_UNAVAILABLE;
-
-@end
-
-NS_ASSUME_NONNULL_END
+#import "api/peerconnection/RTCRtpReceiver.h"