Implement new optional parameters syntax in the vm (issue 4290).

tests/language/type_vm_test.dart

 // Copyright (c) 2011, 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.
 // VMOptions=--enable_type_checks --no_show_internal_names
 //
 // Dart test program testing type checks.
 
 class TypeTest {
   static test() {
     int result = 0;
@@ skipping 154 matching lines @@
       Expect.equals("type_vm_test.dart", subs);
       Expect.equals(145, error.line);
       Expect.equals(33, error.column);
     }
     return result;
   }
 
   static testFunctionNum() {
     int result = 0;
     Function anyFunction;
-    void acceptFunNum(void funNum(num num)) { };
+    void acceptFunNum(void funNum(num n)) { };
     void funObj(Object obj) { };
-    void funNum(num num) { };
+    void funNum(num n) { };
     void funInt(int i) { };
     void funString(String s) { };
     anyFunction = funObj;  // No error.
     anyFunction = funNum;  // No error.
     anyFunction = funInt;  // No error.
     anyFunction = funString;  // No error.
     acceptFunNum(funObj);  // No error.
     acceptFunNum(funNum);  // No error.
     acceptFunNum(funInt);  // No error.
     try {
@@ skipping 370 matching lines @@
 class C {
   factory C() {
     return 1;  // Implicit result type is 'C', not int.
   }
 }
 
 
 main() {
   TypeTest.testMain();
 }