Fix tonic include guards

tonic/dart_string_cache.h

 // Copyright 2015 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.
 
-#ifndef SKY_ENGINE_TONIC_DART_STRING_CACHE_H_
-#define SKY_ENGINE_TONIC_DART_STRING_CACHE_H_
+#ifndef TONIC_DART_STRING_CACHE_H_
+#define TONIC_DART_STRING_CACHE_H_
 
 #include "base/logging.h"
 #include "dart/runtime/include/dart_api.h"
 #include "sky/engine/wtf/HashMap.h"
 #include "sky/engine/wtf/RefPtr.h"
 #include "sky/engine/wtf/text/StringHash.h"
 #include "sky/engine/wtf/text/StringImpl.h"
 
 namespace tonic {
 
@@ skipping 21 matching lines @@
 
   StringCache cache_;
   Dart_WeakPersistentHandle last_dart_string_;
   RefPtr<StringImpl> last_string_impl_;
 
   DISALLOW_COPY_AND_ASSIGN(DartStringCache);
 };
 
 }  // namespace tonic
 
-#endif  // SKY_ENGINE_TONIC_DART_STRING_CACHE_H_
+#endif  // TONIC_DART_STRING_CACHE_H_