Update boilerplate.py to add ARC header guards to iOS ObjCpp files.

tools/boilerplate.py

 #!/usr/bin/env python
 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Create files with copyright boilerplate and header include guards.
 
 Usage: tools/boilerplate.py path/to/file.{h,cc}
 """
 
@@ skipping 42 matching lines @@
 
 def _RemoveTestSuffix(filename):
   base, _ = os.path.splitext(filename)
   suffixes = [ '_test', '_unittest', '_browsertest' ]
   for suffix in suffixes:
     l = len(suffix)
     if base[-l:] == suffix:
       return base[:-l]
   return base
 
+
+def _IsIOSFile(filename):
+  if os.path.splitext(os.path.basename(filename))[0].endswith('_ios'):
+    return True
+  if 'ios' in filename.split(os.path.sep):
+    return True
+  return False
+
+
 def _CppImplementation(filename):
   return '\n#include "' + _RemoveTestSuffix(filename) + '.h"\n'
 
 
 def _ObjCppImplementation(filename):
-  return '\n#import "' + _RemoveTestSuffix(filename) + '.h"\n'
+  implementation = '\n#import "' + _RemoveTestSuffix(filename) + '.h"\n'
+  if not _IsIOSFile(filename):
+    return implementation
+  implementation += '\n'
+  implementation += '#if !defined(__has_feature) || !__has_feature(objc_arc)\n'
+  implementation += '#error "This file requires ARC support."\n'
+  implementation += '#endif\n'
+  return implementation
 
 
 def _CreateFile(filename):
   contents = _GetHeader(filename) + '\n'
 
   if filename.endswith('.h'):
     contents += _CppHeader(filename)
   elif filename.endswith('.cc'):
     contents += _CppImplementation(filename)
   elif filename.endswith('.mm'):
@@ skipping 20 matching lines @@
     if os.path.exists(f):
       print >> sys.stderr, 'A file at path %s already exists' % f
       return 2
 
   for f in files:
     _CreateFile(f)
 
 
 if __name__ == '__main__':
   sys.exit(Main())