Use NativesFlag to allow/disallow natives syntax during compilation.

src/compiler.h

 // Copyright 2010 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 62 matching lines @@
   void MarkAsStrict() {
     flags_ |= IsStrict::encode(true);
   }
   StrictModeFlag StrictMode() {
     return is_strict() ? kStrictMode : kNonStrictMode;
   }
   void MarkAsInLoop() {
     ASSERT(is_lazy());
     flags_ |= IsInLoop::encode(true);
   }
+  void MarkAsAllowingNativesSyntax() {
+    flags_ |= IsNativesSyntaxAllowed::encode(true);
+  }
+  bool allows_natives_syntax() const {
+    return IsNativesSyntaxAllowed::decode(flags_);
+  }
   void SetFunction(FunctionLiteral* literal) {
     ASSERT(function_ == NULL);
     function_ = literal;
   }
   void SetScope(Scope* scope) {
     ASSERT(scope_ == NULL);
     scope_ = scope;
   }
   void SetCode(Handle<Code> code) { code_ = code; }
   void SetExtension(v8::Extension* extension) {
@@ skipping 74 matching lines @@
   //
   // Compilation is either eager or lazy.
   class IsLazy:   public BitField<bool, 0, 1> {};
   // Flags that can be set for eager compilation.
   class IsEval:   public BitField<bool, 1, 1> {};
   class IsGlobal: public BitField<bool, 2, 1> {};
   // Flags that can be set for lazy compilation.
   class IsInLoop: public BitField<bool, 3, 1> {};
   // Strict mode - used in eager compilation.
   class IsStrict: public BitField<bool, 4, 1> {};
+  // Native syntax (%-stuff) allowed?
+  class IsNativesSyntaxAllowed: public BitField<bool, 5, 1> {};
 
   unsigned flags_;
 
   // Fields filled in by the compilation pipeline.
   // AST filled in by the parser.
   FunctionLiteral* function_;
   // The scope of the function literal as a convenience.  Set to indicate
   // that scopes have been analyzed.
   Scope* scope_;
   // The compiled code.
@@ skipping 94 matching lines @@
       FrameElement::ClearConstantList();
       Result::ClearConstantList();
     }
   }
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_COMPILER_H_