Properly export the symbols of video frame-buffer classes for link-time

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

 /*
  *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 47 matching lines @@
 
 /** Protocol for RTCYUVPlanarBuffers containing I420 data */
 @protocol RTCI420Buffer <RTCYUVPlanarBuffer>
 @end
 
 /** Extension of the I420 buffer with mutable data access */
 @protocol RTCMutableI420Buffer <RTCI420Buffer, RTCMutableYUVPlanarBuffer>
 @end
 
 /** RTCVideoFrameBuffer containing a CVPixelBufferRef */
+RTC_EXPORT
 @interface RTCCVPixelBuffer : NSObject <RTCVideoFrameBuffer>
 
 @property(nonatomic, readonly) CVPixelBufferRef pixelBuffer;
 
 - (instancetype)initWithPixelBuffer:(CVPixelBufferRef)pixelBuffer;
 - (instancetype)initWithPixelBuffer:(CVPixelBufferRef)pixelBuffer
                        adaptedWidth:(int)adaptedWidth
                       adaptedHeight:(int)adaptedHeight
                           cropWidth:(int)cropWidth
                          cropHeight:(int)cropHeight
                               cropX:(int)cropX
                               cropY:(int)cropY;
 
 - (BOOL)requiresCropping;
 - (BOOL)requiresScalingToWidth:(int)width height:(int)height;
 - (int)bufferSizeForCroppingAndScalingToWidth:(int)width height:(int)height;
 /** The minimum size of the |tmpBuffer| must be the number of bytes returned from the
  * bufferSizeForCroppingAndScalingToWidth:height: method.
  */
 - (BOOL)cropAndScaleTo:(CVPixelBufferRef)outputPixelBuffer withTempBuffer:(uint8_t *)tmpBuffer;
 
 @end
 
 /** RTCI420Buffer implements the RTCI420Buffer protocol */
+RTC_EXPORT
 @interface RTCI420Buffer : NSObject <RTCI420Buffer>
 @end
 
 /** Mutable version of RTCI420Buffer */
+RTC_EXPORT
 @interface RTCMutableI420Buffer : RTCI420Buffer <RTCMutableI420Buffer>
 @end
 
 NS_ASSUME_NONNULL_END