Fix tonic include guards

tonic/dart_converter.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_CONVERTER_H_
-#define SKY_ENGINE_TONIC_DART_CONVERTER_H_
+#ifndef TONIC_DART_CONVERTER_H_
+#define TONIC_DART_CONVERTER_H_
 
 #include <string>
 
 #include "tonic/dart_state.h"
 
 namespace tonic {
 
 // DartConvert converts types back and forth from Sky to Dart. The template
 // parameter |T| determines what kind of type conversion to perform.
 template <typename T, typename Enable = void>
@@ skipping 176 matching lines @@
 }
 
 
 // Alias Dart_NewStringFromCString for less typing.
 inline Dart_Handle ToDart(const char* val) {
   return Dart_NewStringFromCString(val);
 }
 
 }  // namespace tonic
 
-#endif  // SKY_ENGINE_TONIC_DART_CONVERTER_H_
+#endif  // TONIC_DART_CONVERTER_H_