Update/move RTCVideoRendererAdapter to webrtc/api/objc.

webrtc/api/objc/RTCVideoRendererAdapter.h

Index: webrtc/api/objc/RTCVideoRendererAdapter.h
diff --git a/webrtc/api/objc/RTCMediaSource.h b/webrtc/api/objc/RTCVideoRendererAdapter.h
similarity index 63%
copy from webrtc/api/objc/RTCMediaSource.h
copy to webrtc/api/objc/RTCVideoRendererAdapter.h
index 0b36b8d7093543c803f6097d28488efef8678306..434a61b2bd0c8f86d04f733045262d4303fd8f84 100644
--- a/webrtc/api/objc/RTCMediaSource.h
+++ b/webrtc/api/objc/RTCVideoRendererAdapter.h
@@ -10,19 +10,15 @@
 
 #import <Foundation/Foundation.h>
 
-typedef NS_ENUM(NSInteger, RTCSourceState) {
-  RTCSourceStateInitializing,
-  RTCSourceStateLive,
-  RTCSourceStateEnded,
-  RTCSourceStateMuted,
-};
-
 NS_ASSUME_NONNULL_BEGIN
 
-@interface RTCMediaSource : NSObject
-
-/** The current state of the RTCMediaSource. */
-@property(nonatomic, readonly) RTCSourceState state;
+/*
+ * Creates a webrtc::VideoRendererInterface surface for an RTCVideoRenderer. The
+ * webrtc::VideoRendererInterface is used by WebRTC rendering code - this
+ * adapter adapts calls made to that interface to the RTCVideoRenderer supplied
+ * during construction.
+ */
+@interface RTCVideoRendererAdapter : NSObject
 
 - (instancetype)init NS_UNAVAILABLE;