Add optional arguments to our indexOf/lastIndexOf methods.

runtime/lib/growable_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 GrowableObjectArray<T> implements List<T> {
   ObjectArray<T> backingArray;
 
   void copyFrom(List<Object> src, int srcStart, int dstStart, int count) {
     Arrays.copy(src, srcStart, this, dstStart, count);
   }
@@ skipping 57 matching lines @@
     Arrays.rangeCheck(this, start, length);
     List list = new List<T>();
     list.length = length;
     Arrays.copy(this, start, list, 0, length);
     return list;
   }
 
   // The length of this growable array. It is always less than the
   // length of the backing array.
   int _length;
-  // Constant used by indexOf and lastIndexOf when the element given
-  // is not in the array.
-  static final int ABSENT = -1;
 
   GrowableObjectArray()
       : _length = 0, backingArray = new ObjectArray<T>(4) {}
 
   GrowableObjectArray.withCapacity(int capacity) {
     _length = 0;
     if (capacity <= 0) {
       capacity = 4;
     }
     backingArray = new ObjectArray<T>(capacity);
@@ skipping 74 matching lines @@
     return backingArray[_length];
   }
 
   T last() {
     if (_length === 0) {
       throw new IndexOutOfRangeException(-1);
     }
     return backingArray[_length - 1];
   }
 
-  int indexOf(T element, int startIndex) {
-    return Arrays.indexOf(backingArray, element, startIndex, _length);
+  int indexOf(T element, [int start = 0]) {
+    return Arrays.indexOf(backingArray, element, start, _length);
   }
 
-  int lastIndexOf(T element, int startIndex) {
-    return Arrays.lastIndexOf(backingArray, element, startIndex);
+  int lastIndexOf(T element, [int start = null]) {
+    if (start === null) start = length - 1;
+    return Arrays.lastIndexOf(backingArray, element, start);
   }
 
   /**
    * Collection interface.
    */
 
   void forEach(f(T element)) {
     // TODO(srdjan): Use Collections.forEach(this, f);
     // Using backingArray directly improves DeltaBlue performance by 25%.
     for (int i = 0; i < _length; i++) {
@@ skipping 45 matching lines @@
     if (!hasNext()) {
       throw const NoMoreElementsException();
     }
     return _array[_pos++];
   }
 
   final GrowableObjectArray<T> _array;
   int _pos;
 }