Harden a few builtins

src/debug-debugger.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Default number of frames to include in the response to backtrace request.
 var kDefaultBacktraceLength = 10;
 
 var Debug = {};
 
 // Regular expression to skip "crud" at the beginning of a source line which is
@@ skipping 2467 matching lines @@
 DebugCommandProcessor.prototype.isRunning = function() {
   return this.running_;
 };
 
 
 DebugCommandProcessor.prototype.systemBreak = function(cmd, args) {
   return %SystemBreak();
 };
 
 
-function NumberToHex8Str(n) {
-  var r = "";
-  for (var i = 0; i < 8; ++i) {
-    var c = hexCharArray[n & 0x0F];  // hexCharArray is defined in uri.js
-    r = c + r;
-    n = n >>> 4;
-  }
-  return r;
-}
-
-
 /**
  * Convert an Object to its debugger protocol representation. The representation
  * may be serilized to a JSON object using JSON.stringify().
  * This implementation simply runs through all string property names, converts
  * each property value to a protocol value and adds the property to the result
  * object. For type "object" the function will be called recursively. Note that
  * circular structures will cause infinite recursion.
  * @param {Object} object The object to format as protocol object.
  * @param {MirrorSerializer} mirror_serializer The serializer to use if any
  *     mirror objects are encountered.
@@ skipping 64 matching lines @@
 
     default:
       json = null;
   }
   return json;
 }
 
 Debug.TestApi = {
   CommandProcessorResolveValue: DebugCommandProcessor.resolveValue_
 };