iOS/MacOS:Refactor metal rendering by extracting common implementation

webrtc/sdk/objc/Framework/Classes/Metal/RTCMTLRenderer+Private.h

Index: webrtc/sdk/objc/Framework/Classes/Metal/RTCMTLRenderer+Private.h
diff --git a/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMTLNSVideoView.h b/webrtc/sdk/objc/Framework/Classes/Metal/RTCMTLRenderer+Private.h
similarity index 54%
copy from webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMTLNSVideoView.h
copy to webrtc/sdk/objc/Framework/Classes/Metal/RTCMTLRenderer+Private.h
index ba4880ff9472326878c9dfe88cce4f37656c0e02..dfeb87b5fe55cfb380f10ecc5afeec869af7adc4 100644
--- a/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMTLNSVideoView.h
+++ b/webrtc/sdk/objc/Framework/Classes/Metal/RTCMTLRenderer+Private.h
@@ -8,10 +8,14 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#import <Cocoa/Cocoa.h>
-#import "WebRTC/RTCVideoRenderer.h"
-
-NS_AVAILABLE_MAC(10.11)
-@interface RTCMTLNSVideoView : NSView <RTCVideoRenderer>
+#import <Metal/Metal.h>
+#import "RTCMTLRenderer.h"
 
+NS_ASSUME_NONNULL_BEGIN
+@interface RTCMTLRenderer (Private)
+- (nullable id<MTLDevice>)currentMetalDevice;
+- (NSString *)shaderSource;
+- (BOOL)setupTexturesForFrame:(nonnull RTCVideoFrame *)frame;
+- (void)uploadTexturesToRenderEncoder:(id<MTLRenderCommandEncoder>)renderEncoder;
 @end
+NS_ASSUME_NONNULL_END