Use NativesFlag to allow/disallow natives syntax during compilation.

src/debug.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 746 matching lines @@
   if (index == -1) {
     return false;
   }
 
   // Find source and name for the requested script.
   Handle<String> source_code = Bootstrapper::NativesSourceLookup(index);
   Vector<const char> name = Natives::GetScriptName(index);
   Handle<String> script_name = Factory::NewStringFromAscii(name);
 
   // Compile the script.
-  bool allow_natives_syntax = FLAG_allow_natives_syntax;
-  FLAG_allow_natives_syntax = true;
   Handle<SharedFunctionInfo> function_info;
   function_info = Compiler::Compile(source_code,
                                     script_name,
                                     0, 0, NULL, NULL,
                                     Handle<String>::null(),
                                     NATIVES_CODE);
-  FLAG_allow_natives_syntax = allow_natives_syntax;
 
   // Silently ignore stack overflows during compilation.
   if (function_info.is_null()) {
     ASSERT(Top::has_pending_exception());
     Top::clear_pending_exception();
     return false;
   }
 
   // Execute the shared function in the debugger context.
   Handle<Context> context = Top::global_context();
@@ skipping 2293 matching lines @@
     {
       Locker locker;
       Debugger::CallMessageDispatchHandler();
     }
   }
 }
 
 #endif  // ENABLE_DEBUGGER_SUPPORT
 
 } }  // namespace v8::internal