Use destructuring assignments for named parameters (#180)

test/codegen/methods.dart

 // Copyright (c) 2015, 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 methods;
 
 class A {
   int x() => 42;
 
   int y(int a) {
     return a;
   }
 
   int z([num b]) => b;
 
   int zz([int b = 0]) => b;
 
   int w(int a, {num b}) {
     return a + b;
   }
 
-  int ww(int a, {int b: 0}) {
-    return a + b;
-  }
+  clashWithObjectProperty({constructor}) => constructor;
+  clashWithJsReservedName({function}) => function;
 
   int get a => x();
 
   void set b(int b) {}
 
   int _c = 3;
 
   int get c => _c;
 
   void set c(int c) {
@@ skipping 22 matching lines @@
   var h = aa.x;
 
   // Tear-off of object methods
   var ts = a.toString;
   var nsm = a.noSuchMethod;
 
   // Tear-off extension methods
   var c = "".padLeft;
   var r = (3.0).floor;
 }