Add optional arguments to our indexOf/lastIndexOf methods.

client/dom/generated/src/wrapping/_MediaListWrappingImplementation.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.
 
 // WARNING: Do not edit - generated code.
 
 class _MediaListWrappingImplementation extends DOMWrapperBase implements MediaList {
   _MediaListWrappingImplementation() : super() {}
 
   static create__MediaListWrappingImplementation() native {
@@ skipping 30 matching lines @@
   }
 
   void sort(int compare(String a, String b)) {
     throw new UnsupportedOperationException("Cannot sort immutable List.");
   }
 
   void copyFrom(List<Object> src, int srcStart, int dstStart, int count) {
     throw new UnsupportedOperationException("This object is immutable.");
   }
 
-  int indexOf(String element, int startIndex) {
-    return _Lists.indexOf(this, element, startIndex, this.length);
+  int indexOf(String element, [int start = 0]) {
+    return _Lists.indexOf(this, element, start, this.length);
   }
 
-  int lastIndexOf(String element, int startIndex) {
-    return _Lists.lastIndexOf(this, element, startIndex);
+  int lastIndexOf(String element, [int start = null]) {
+    if (start === null) start = length - 1;
+    return _Lists.lastIndexOf(this, element, start);
   }
 
   int clear() {
     throw new UnsupportedOperationException("Cannot clear immutable List.");
   }
 
   String removeLast() {
     throw new UnsupportedOperationException("Cannot removeLast on immutable List.");
   }
 
@@ skipping 53 matching lines @@
   }
   static void _deleteMedium(receiver, oldMedium) native;
 
   String item(int index) {
     return _item(this, index);
   }
   static String _item(receiver, index) native;
 
   String get typeName() { return "MediaList"; }
 }