Enable "strict mode"; for debugger scripts

src/mirror-debugger.js

 // Copyright 2006-2012 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.
+"use strict";
 
 // Handle id counters.
 var next_handle_ = 0;
 var next_transient_handle_ = -1;
 
 // Mirror cache.
 var mirror_cache_ = [];
 var mirror_cache_enabled_ = true;
 
 
@@ skipping 23 matching lines @@
  * @param {value or Object} value the value or object to retreive the mirror for
  * @param {boolean} transient indicate whether this object is transient and
  *    should not be added to the mirror cache. The default is not transient.
  * @returns {Mirror} the mirror reflects the passed value or object
  */
 function MakeMirror(value, opt_transient) {
   var mirror;
 
   // Look for non transient mirrors in the mirror cache.
   if (!opt_transient && mirror_cache_enabled_) {
-    for (id in mirror_cache_) {
+    for (var id in mirror_cache_) {
       mirror = mirror_cache_[id];
       if (mirror.value() === value) {
         return mirror;
       }
       // Special check for NaN as NaN == NaN is false.
       if (mirror.isNumber() && isNaN(mirror.value()) &&
           typeof value == 'number' && isNaN(value)) {
         return mirror;
       }
     }
@@ skipping 1223 matching lines @@
  */
 ErrorMirror.prototype.message = function() {
   return this.value_.message;
 };
 
 
 ErrorMirror.prototype.toText = function() {
   // Use the same text representation as in messages.js.
   var text;
   try {
-    str = %_CallFunction(this.value_, builtins.ErrorToString);
+    text = %_CallFunction(this.value_, builtins.ErrorToString);
   } catch (e) {
-    str = '#<Error>';
+    text = '#<Error>';
   }
-  return str;
+  return text;
 };
 
 
 /**
  * Mirror object for a Promise object.
  * @param {Object} value The Promise object
  * @constructor
  * @extends ObjectMirror
  */
 function PromiseMirror(value) {
@@ skipping 1728 matching lines @@
   }
   if (!NUMBER_IS_FINITE(value)) {
     if (value > 0) {
       return 'Infinity';
     } else {
       return '-Infinity';
     }
   }
   return value;
 }