Remove use of PCH files in webrtc/sdk/objc

webrtc/sdk/objc/Framework/Classes/RTCNSGLVideoView.m

 /*
  *  Copyright 2015 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.
  */
 
+#import <Foundation/Foundation.h>
+
 #if !TARGET_OS_IPHONE
 
 #import "WebRTC/RTCNSGLVideoView.h"
 
 #import <CoreVideo/CVDisplayLink.h>
 #import <OpenGL/gl3.h>
 
 #import "RTCOpenGLVideoRenderer.h"
 #import "WebRTC/RTCVideoFrame.h"
 
@@ skipping 116 matching lines @@
   if (!_displayLink) {
     return;
   }
   CVDisplayLinkRelease(_displayLink);
   _displayLink = NULL;
 }
 
 @end
 
 #endif  // !TARGET_OS_IPHONE