Remove use of PCH files in webrtc/sdk/objc

webrtc/sdk/objc/WebRTC-Prefix.pch

Index: webrtc/sdk/objc/WebRTC-Prefix.pch
diff --git a/webrtc/sdk/objc/WebRTC-Prefix.pch b/webrtc/sdk/objc/WebRTC-Prefix.pch
deleted file mode 100644
index c56cb48ab872ea7d27a83b964c0d776ec118ef98..0000000000000000000000000000000000000000
--- a/webrtc/sdk/objc/WebRTC-Prefix.pch
+++ /dev/null
@@ -1,36 +0,0 @@
-/*
- *  Copyright 2016 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.
- */
-
-#ifdef __OBJC__
-
-#if !defined(__has_feature) || !__has_feature(objc_arc)
-#error "This file requires ARC support."
-#endif
-
-#if !defined(__has_feature) || !__has_feature(nullability)
-#error "This file requires nullability support."
-#endif
-
-#import <Foundation/Foundation.h>
-
-// The following nonnull macros were introduced in OSX SDK 10.10.3. However,
-// the bots appear to be running something older. We define them here if they
-// aren't already defined in NSObjCRuntime.h, which is included by
-// Foundation/Foundation.h.
-
-#if !defined(NS_ASSUME_NONNULL_BEGIN)
-#define NS_ASSUME_NONNULL_BEGIN
-#endif
-
-#if !defined(NS_ASSUME_NONNULL_END)
-#define NS_ASSUME_NONNULL_END
-#endif
-
-#endif  // __OBJC__