Add optional arguments to our indexOf/lastIndexOf methods.

runtime/lib/array.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.
 
 class ListFactory<T> {
 
   factory List.from(Iterable<T> other) {
     GrowableObjectArray<T> list = new GrowableObjectArray<T>();
     for (final e in other) {
       list.add(e);
@@ skipping 98 matching lines @@
   }
 
   bool isEmpty() {
     return this.length === 0;
   }
 
   void sort(int compare(T a, T b)) {
     DualPivotQuicksort.sort(this, compare);
   }
 
-  int indexOf(T element, int startIndex) {
-    return Arrays.indexOf(this, element, startIndex, this.length);
+  int indexOf(T element, [int start = 0]) {
+    return Arrays.indexOf(this, element, start, this.length);
   }
 
-  int lastIndexOf(T element, int startIndex) {
-    return Arrays.lastIndexOf(this, element, startIndex);
+  int lastIndexOf(T element, [int start = null]) {
+    if (start === null) start = length - 1;
+    return Arrays.lastIndexOf(this, element, start);
   }
 
   Iterator<T> iterator() {
     return new FixedSizeArrayIterator<T>(this);
   }
 
   void add(T element) {
     throw const UnsupportedOperationException(
         "Cannot add to a non-extendable array");
   }
@@ skipping 101 matching lines @@
 
   void sort(int compare(T a, T b)) {
     throw const UnsupportedOperationException(
         "Cannot modify an immutable array");
   }
 
   String toString() {
     return "ImmutableArray";
   }
 
-  int indexOf(T element, int startIndex) {
-    return Arrays.indexOf(this, element, startIndex, this.length);
+  int indexOf(T element, [int start = 0]) {
+    return Arrays.indexOf(this, element, start, this.length);
   }
 
-  int lastIndexOf(T element, int startIndex) {
-    return Arrays.lastIndexOf(this, element, startIndex);
+  int lastIndexOf(T element, [int start = null]) {
+    if (start === null) start = length - 1;
+    return Arrays.lastIndexOf(this, element, start);
   }
 
   Iterator<T> iterator() {
     return new FixedSizeArrayIterator<T>(this);
   }
 
   void add(T element) {
     throw const UnsupportedOperationException(
         "Cannot add to an immutable array");
   }
@@ skipping 43 matching lines @@
     if (!hasNext()) {
       throw const NoMoreElementsException();
     }
     return _array[_pos++];
   }
 
   final List<T> _array;
   final int _length;  // Cache array length for faster access.
   int _pos;
 }