Lock the prototype of internal classes.

src/string.js

 // Copyright 2006-2009 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 893 matching lines @@
 // ReplaceResultBuilder support.
 function ReplaceResultBuilder(str) {
   if (%_ArgumentsLength() > 1) {
     this.elements = %_Arguments(1);
   } else {
     this.elements = new InternalArray();
   }
   this.special_string = str;
 }
 
-ReplaceResultBuilder.prototype.__proto__ = null;
-
-
-ReplaceResultBuilder.prototype.add = function(str) {
-  str = TO_STRING_INLINE(str);
-  if (str.length > 0) this.elements.push(str);
-}
-
-
-ReplaceResultBuilder.prototype.addSpecialSlice = function(start, end) {
-  var len = end - start;
-  if (start < 0 || len <= 0) return;
-  if (start < 0x80000 && len < 0x800) {
-    this.elements.push((start << 11) | len);
-  } else {
-    // 0 < len <= String::kMaxLength and Smi::kMaxValue >= String::kMaxLength,
-    // so -len is a smi.
+SetUpLockedPrototype(ReplaceResultBuilder,
+  $Array("elements", "special_string"), $Array(
+  "add", function(str) {
+    str = TO_STRING_INLINE(str);
+    if (str.length > 0) this.elements.push(str);
+  },
+  "addSpecialSlice", function(start, end) {
+    var len = end - start;
+    if (start < 0 || len <= 0) return;
+    if (start < 0x80000 && len < 0x800) {
+      this.elements.push((start << 11) | len);
+    } else {
+      // 0 < len <= String::kMaxLength and Smi::kMaxValue >= String::kMaxLength,
+      // so -len is a smi.
+      var elements = this.elements;
+      elements.push(-len);
+      elements.push(start);
+    }
+  },
+  "generate", function() {
     var elements = this.elements;
-    elements.push(-len);
-    elements.push(start);
+    return %StringBuilderConcat(elements, elements.length, this.special_string);
   }
-}
-
-
-ReplaceResultBuilder.prototype.generate = function() {
-  var elements = this.elements;
-  return %StringBuilderConcat(elements, elements.length, this.special_string);
-}
+));
 
 
 // -------------------------------------------------------------------
 
-function SetupString() {
-  // Setup the constructor property on the String prototype object.
+function SetUpString() {
+  %CheckIsBootstrapping();
+  // Set up the constructor property on the String prototype object.
   %SetProperty($String.prototype, "constructor", $String, DONT_ENUM);
 
 
-  // Setup the non-enumerable functions on the String object.
+  // Set up the non-enumerable functions on the String object.
   InstallFunctions($String, DONT_ENUM, $Array(
     "fromCharCode", StringFromCharCode
   ));
 
 
-  // Setup the non-enumerable functions on the String prototype object.
+  // Set up the non-enumerable functions on the String prototype object.
   InstallFunctionsOnHiddenPrototype($String.prototype, DONT_ENUM, $Array(
     "valueOf", StringValueOf,
     "toString", StringToString,
     "charAt", StringCharAt,
     "charCodeAt", StringCharCodeAt,
     "concat", StringConcat,
     "indexOf", StringIndexOf,
     "lastIndexOf", StringLastIndexOf,
     "localeCompare", StringLocaleCompare,
     "match", StringMatch,
@@ skipping 19 matching lines @@
     "bold", StringBold,
     "fixed", StringFixed,
     "italics", StringItalics,
     "small", StringSmall,
     "strike", StringStrike,
     "sub", StringSub,
     "sup", StringSup
   ));
 }
 
-
-SetupString();
+SetUpString();