This CL adds support for extension in GYP.

test/ios/extension/ActionExtension/ActionViewController.h

Index: test/ios/extension/ActionExtension/ActionViewController.h
diff --git a/test/win/linker-flags/safeseh_hello.cc b/test/ios/extension/ActionExtension/ActionViewController.h
similarity index 66%
copy from test/win/linker-flags/safeseh_hello.cc
copy to test/ios/extension/ActionExtension/ActionViewController.h
index 6141300d2c0a517a8f79075619d089be0ddbf2ea..1c9250902961835864d540a38e19ebe03a6c9f38 100644
--- a/test/win/linker-flags/safeseh_hello.cc
+++ b/test/ios/extension/ActionExtension/ActionViewController.h
@@ -2,10 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-extern "C" {
-int zero(void);
-}
+#import <UIKit/UIKit.h>
 
-int main() {
-  return zero();
-}
+@interface ActionViewController : UIViewController
+
+@end