Workaround: Render PixelBuffer in RTCMTLVideoView (#58)

* workaround for iOS also

* comment

sdk/objc/components/renderer/metal/RTCMTLVideoView.m

@@ -271,18 +271,15 @@ - (void)renderFrame:(nullable RTC_OBJC_TYPE(RTCVideoFrame) *)frame {
     return;
   }
 
-#if TARGET_OS_IPHONE
-  self.videoFrame = frame;
-#elif TARGET_OS_OSX
-  // Rendering native CVPixelBuffer is not supported on OS X.
+  // Workaround to support RTCCVPixelBuffer rendering.
+  // RTCMTLRGBRenderer seems to be broken at the moment.
   BOOL useI420 = NO;
   if ([frame.buffer isKindOfClass:[RTC_OBJC_TYPE(RTCCVPixelBuffer) class]]) {
     RTC_OBJC_TYPE(RTCCVPixelBuffer) *buffer = (RTC_OBJC_TYPE(RTCCVPixelBuffer) *)frame.buffer;
     const OSType pixelFormat = CVPixelBufferGetPixelFormatType(buffer.pixelBuffer);
     useI420 = pixelFormat == kCVPixelFormatType_32BGRA || pixelFormat == kCVPixelFormatType_32ARGB;
   }
   self.videoFrame = useI420 ? [frame newI420VideoFrame] : frame;
-#endif
 }
 
 #pragma mark - Cross platform