Do not generate calls to Dart_EnterScope/Dart_ExitScope around native

tools/dom/scripts/systemnative.py

 #!/usr/bin/python
 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 """This module provides shared functionality for the systems to generate
 native binding from the IDL database."""
 
 import emitter
 import os
@@ skipping 699 matching lines @@
           '        if (!RuntimeEnabledFeatures::$(FEATURE)Enabled()) {\n'
           '            exception = Dart_NewStringFromCString("Feature $FEATURE is not enabled");\n'
           '            goto fail;\n'
           '        }',
           FEATURE=self._ToWebKitName(v8EnabledAtRuntime))
 
     body_emitter = self._cpp_definitions_emitter.Emit(
         '\n'
         'static void $CALLBACK_NAME(Dart_NativeArguments args)\n'
         '{\n'
-        '    DartApiScope dartApiScope;\n'
         '$!BODY'
         '}\n',
         CALLBACK_NAME=callback_name)
 
     if raises_exceptions:
       body_emitter = body_emitter.Emit(
           '    Dart_Handle exception = 0;\n'
           '$!BODY'
           '\n'
           'fail:\n'
@@ skipping 333 matching lines @@
             '    if (Dart_NativeFunction func = $CLASS_NAME::resolver(name, argumentCount))\n'
             '        return func;\n',
             CLASS_NAME=os.path.splitext(os.path.basename(path))[0])
 
 def _IsOptionalStringArgumentInInitEventMethod(interface, operation, argument):
   return (
       interface.id.endswith('Event') and
       operation.id.startswith('init') and
       argument.ext_attrs.get('Default') == 'Undefined' and
       argument.type.id == 'DOMString')