Fix the new dart2dart backend.

pkg/compiler/lib/src/dart_backend/backend_ast_emitter.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.
 
 library backend_ast_emitter;
 
 import '../tree_ir/tree_ir_nodes.dart' as tree;
 import 'backend_ast_nodes.dart';
 import '../constants/expressions.dart';
 import '../constants/values.dart';
@@ skipping 59 matching lines @@
       : this.parent = parent,
         usedVariableNames = parent.usedVariableNames;
 
   FunctionExpression emit(tree.FunctionDefinition definition) {
     functionElement = definition.element;
 
     Parameters parameters = emitRootParameters(definition);
 
     // Declare parameters.
     for (tree.Variable param in definition.parameters) {
-      getVariableName(param);
+      variableNames[param] = param.element.name;
+      usedVariableNames.add(param.element.name);
       declaredVariables.add(param);
     }
 
     Statement body;
     if (definition.isAbstract) {
       body = new EmptyStatement();
     } else {
       firstStatement = definition.body;
       visitStatement(definition.body);
       removeTrailingReturn();
@@ skipping 818 matching lines @@
       : super(name, ElementKind.VARIABLE, enclosingElement, variables, null);
 
   ExecutableElement get executableContext => enclosingElement;
 
   ExecutableElement get memberContext => executableContext.memberContext;
 
   bool get isLocal => true;
 
   LibraryElement get implementationLibrary => enclosingElement.library;
 }