ObjC: Remove RTCVideoFrame.nativeHandle

Access to a native buffer should be through RTCVideoFrame.buffer
instead.

BUG=webrtc:7785

Review-Url: https://codereview.webrtc.org/2990253002
Cr-Commit-Position: refs/heads/master@{#19430}

webrtc/sdk/objc/Framework/Classes/PeerConnection/RTCVideoFrame.mm

@@ -83,14 +83,6 @@
   return _timeStampNs;
 }
 
-- (CVPixelBufferRef)nativeHandle {
-  if ([_buffer isKindOfClass:[RTCCVPixelBuffer class]]) {
-    return ((RTCCVPixelBuffer *)_buffer).pixelBuffer;
-  } else {
-    return nullptr;
-  }
-}
-
 - (RTCVideoFrame *)newI420VideoFrame {
   return [[RTCVideoFrame alloc] initWithBuffer:[_buffer toI420]
                                       rotation:_rotation

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

@@ -54,10 +54,6 @@ RTC_EXPORT
 /** Timestamp 90 kHz. */
 @property(nonatomic, assign) int32_t timeStamp;
 
-/** The native handle should be a pixel buffer on iOS. */
-@property(nonatomic, readonly)
-    CVPixelBufferRef nativeHandle DEPRECATED_MSG_ATTRIBUTE("use buffer instead");
-
 @property(nonatomic, readonly) id<RTCVideoFrameBuffer> buffer;
 
 - (instancetype)init NS_UNAVAILABLE;