Add dead CodeRegionTable for tracking overwritten Dart code

runtime/bin/vmservice/client/lib/src/service/cache.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of service;
 
 /// Abstract [ServiceObjectCache].
 abstract class ServiceObjectCache<T extends ServiceObject> {
   final Isolate isolate;
   final _cache = new ObservableMap<String, T>();
@@ skipping 99 matching lines @@
     return codeList;
   }
 
   void _resetProfileData() {
     _cache.forEach((k, Code code) {
       code.resetProfileData();
     });
   }
 
   void _updateProfileData(ServiceMap profile, List<Code> codeTable) {
-    var codes = profile['codes'];
+    var codeRegions = profile['codes'];
     var sampleCount = profile['samples'];
-    for (var profileCode in codes) {
-      Code code = profileCode['code'];
-      code.updateProfileData(profileCode, codeTable, sampleCount);
+    for (var codeRegion in codeRegions) {
+      Code code = codeRegion['code'];
+      code.updateProfileData(codeRegion, codeTable, sampleCount);
     }
   }
 }
 
 class ClassCache extends ServiceObjectCache<ServiceMap> {
   ClassCache(Isolate isolate) : super(isolate);
 
   bool cachesId(String id) => _matcher.hasMatch(id);
   bool cachesType(String type) => ServiceObject.stripRef(type) == 'Class';
   ServiceMap _upgrade(ObservableMap obj) =>
       new ServiceMap.fromMap(isolate, obj);
 
   static final RegExp _matcher = new RegExp(r'classes/\d+$');
 }