Remove use of PCH files in webrtc/sdk/objc

A decision has been made to not use prefix header files.

BUG=None

Review-Url: https://codereview.webrtc.org/2590823002
Cr-Commit-Position: refs/heads/master@{#16056}
diff --git a/webrtc/sdk/objc/Framework/Classes/RTCNSGLVideoView.m b/webrtc/sdk/objc/Framework/Classes/RTCNSGLVideoView.m
index 415efe8..18dc4d1 100644
--- a/webrtc/sdk/objc/Framework/Classes/RTCNSGLVideoView.m
+++ b/webrtc/sdk/objc/Framework/Classes/RTCNSGLVideoView.m
@@ -8,6 +8,8 @@
  *  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"
diff --git a/webrtc/sdk/objc/Framework/Classes/RTCShader.h b/webrtc/sdk/objc/Framework/Classes/RTCShader.h
index ac2d0f6..c35a528 100644
--- a/webrtc/sdk/objc/Framework/Classes/RTCShader.h
+++ b/webrtc/sdk/objc/Framework/Classes/RTCShader.h
@@ -8,6 +8,8 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
+#import <Foundation/Foundation.h>
+
 #import "RTCOpenGLDefines.h"
 
 @class RTCVideoFrame;
diff --git a/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCNSGLVideoView.h b/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCNSGLVideoView.h
index d9ed6fb..34588db 100644
--- a/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCNSGLVideoView.h
+++ b/webrtc/sdk/objc/Framework/Headers/WebRTC/RTCNSGLVideoView.h
@@ -8,6 +8,8 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
+#import <Foundation/Foundation.h>
+
 #if !TARGET_OS_IPHONE
 
 #import <AppKit/NSOpenGLView.h>