iOS: Add interface for injecting custom shaders

webrtc/sdk/objc/Framework/Headers/WebRTC/RTCNSGLVideoView.h

Index: webrtc/sdk/objc/Framework/Headers/WebRTC/RTCNSGLVideoView.h
diff --git a/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCNSGLVideoView.h b/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCNSGLVideoView.h
index 34588dbe4ca4f3b23053c99adb0331fd34decd71..9e6a9ce94839c4eb7a9f394b8232ef00041b154b 100644
--- a/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCNSGLVideoView.h
+++ b/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCNSGLVideoView.h
@@ -15,6 +15,7 @@
 #import <AppKit/NSOpenGLView.h>
 
 #import <WebRTC/RTCVideoRenderer.h>
+#import <WebRTC/RTCVideoViewShading.h>
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -29,6 +30,10 @@ NS_ASSUME_NONNULL_BEGIN
 
 @property(nonatomic, weak) id<RTCNSGLVideoViewDelegate> delegate;
 
+- (instancetype)initWithFrame:(NSRect)frameRect
+                  pixelFormat:(NSOpenGLPixelFormat *)format
+                       shader:(id<RTCVideoViewShading>)shader NS_DESIGNATED_INITIALIZER;
+
 @end
 
 NS_ASSUME_NONNULL_END