Do not update original descriptor when building new one.

pkg/compiler/lib/src/js_emitter/old_emitter/reflection_data_parser.dart

 // Copyright (c) 2013, 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 dart2js.js_emitter;
 
 // TODO(ahe): Share these with js_helper.dart.
 const FUNCTION_INDEX = 0;
 const NAME_INDEX = 1;
 const CALL_NAME_INDEX = 2;
@@ skipping 64 matching lines @@
         if (!optionalMethods) {
           newDesc.$methodsWithOptionalArgumentsField = optionalMethods={}
         }
         optionalMethods[property] = previousProperty;
       } else {
         var elem = descriptor[property];
         if (property !== "${namer.classDescriptorProperty}" &&
             elem != null &&
             elem.constructor === Array &&
             property !== "<>") {
-          addStubs(newDesc, elem, property, false, descriptor, []);
+          addStubs(newDesc, elem, property, false, []);
         } else {
           newDesc[previousProperty = property] = elem;
         }
       }
     }
 
     /* The 'fields' are either a constructor function or a
      * string encoding fields, constructor and superclass. Gets the
      * superclass and fields in the format
      *   'Super;field1,field2'
@@ skipping 60 matching lines @@
           if (!optionalMethods) {
             descriptor.$methodsWithOptionalArgumentsField = optionalMethods = {}
           }
           optionalMethods[property] = previousProperty;
         } else if (typeof element === "function") {
           globalObject[previousProperty = property] = element;
           functions.push(property);
           #globalFunctions[property] = element;
         } else if (element.constructor === Array) {
           if (#needsStructuredMemberInfo) {
-            addStubs(globalObject, element, property,
-                     true, descriptor, functions);
+            addStubs(globalObject, element, property, true, functions);
           }
         } else {
           // We will not enter this case if no classes are defined.
           if (#hasClasses) {
             previousProperty = property;
             processClassData(property, element, processedClasses);
           }
         }
       }
     }
 ''', {'typeInformation': typeInformationAccess,
       'globalFunctions': globalFunctionsAccess,
       'hasClasses': oldEmitter.needsClassSupport,
       'needsStructuredMemberInfo': oldEmitter.needsStructuredMemberInfo});
 
 
   /**
    * See [dart2js.js_emitter.ContainerBuilder.addMemberMethod] for format of
    * [array].
    */
   jsAst.Statement addStubs = js.statement('''
-  function addStubs(descriptor, array, name, isStatic,
-                    originalDescriptor, functions) {
+  function addStubs(descriptor, array, name, isStatic, functions) {

[floitsch, 2015/02/26 13:02:54]

while you are at it...

imho descriptor is a really bad name here.
Also add comment what each is.

[herhut, 2015/03/09 13:33:58]

I will do this in a later CL to avoid loads of merge conflicts down the road...

     var index = $FUNCTION_INDEX, alias = array[index], f;
     if (typeof alias == "string") {
       f = array[++index];
     } else {
       f = alias;
       alias = name;
     }
-    var funcs = [originalDescriptor[name] = descriptor[name] =
-        descriptor[alias] = f];
+    var funcs = [descriptor[name] = descriptor[alias] = f];
     f.\$stubName = name;
     functions.push(name);
     for (; index < array.length; index += 2) {
       f = array[index + 1];
       if (typeof f != "function") break;
       f.\$stubName = ${readString("array", "index + 2")};
       funcs.push(f);
       if (f.\$stubName) {
-        originalDescriptor[f.\$stubName] = descriptor[f.\$stubName] = f;
+        descriptor[f.\$stubName] = f;
         functions.push(f.\$stubName);
       }
     }
     index++;
     for (var i = 0; i < funcs.length; index++, i++) {
       funcs[i].\$callName = ${readString("array", "index")};
     }
     var getterStubName = ${readString("array", "index")};
     array = array.slice(++index);
     var requiredParameterInfo = ${readInt("array", "0")};
     var requiredParameterCount = requiredParameterInfo >> 1;
     var isAccessor = (requiredParameterInfo & 1) === 1;
     var isSetter = requiredParameterInfo === 3;
     var isGetter = requiredParameterInfo === 1;
     var optionalParameterInfo = ${readInt("array", "1")};
     var optionalParameterCount = optionalParameterInfo >> 1;
     var optionalParametersAreNamed = (optionalParameterInfo & 1) === 1;
     var isIntercepted =
            requiredParameterCount + optionalParameterCount != funcs[0].length;
     var functionTypeIndex = ${readFunctionType("array", "2")};
     var unmangledNameIndex = $unmangledNameIndex;
 
     if (getterStubName) {
       f = tearOff(funcs, array, isStatic, name, isIntercepted);
       descriptor[name].\$getter = f;
       f.\$getterStub = true;
       // Used to create an isolate using spawnFunction.
       if (isStatic) #globalFunctions[name] = f;
-      originalDescriptor[getterStubName] = descriptor[getterStubName] = f;
+      descriptor[getterStubName] = f;
       funcs.push(f);
       if (getterStubName) functions.push(getterStubName);
       f.\$stubName = getterStubName;
       f.\$callName = null;
       // Update the interceptedNames map (which only exists if `invokeOn` was
       // enabled).
       if (#enabledInvokeOn)
         if (isIntercepted) #interceptedNames[getterStubName] = 1;
     }
 
@@ skipping 237 matching lines @@
 (function() {
   var result = $array[$index];
   if ($check) {
     throw new Error(
         name + ": expected value of type \'$type\' at index " + ($index) +
         " but got " + (typeof result));
   }
   return result;
 })()''';
 }