Add optional arguments to our indexOf/lastIndexOf methods.

compiler/lib/implementation/string.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 StringImplementation implements String native "String" {
   factory StringImplementation.fromValues(List<int> values) {
     return _newFromValues(values);
   }
 
   String operator[](int index) {
@@ skipping 29 matching lines @@
   }
 
   bool endsWith(String other) {
     return substringMatches(length - other.length, other);
   }
 
   bool startsWith(String other) {
     return substringMatches(0, other);
   }
 
-  int indexOf(String other, int startIndex) native;
-  int lastIndexOf(String other, int fromIndex) native;
+  int indexOf(String other, [int start = 0]) {
+    return _nativeIndexOf(other, start);
+  }
+
+  int lastIndexOf(String other, [int start = null]) {
+    if (start === null) start = length - 1;
+    return _nativeLastIndexOf(other, start);
+  }
+
+  int _nativeIndexOf(String other, int start) native;
+  int _nativeLastIndexOf(String other, int start) native;
 
   bool isEmpty() {
     return length == 0;
   }
 
   String concat(String other) native;
 
   String operator +(Object obj) {
     return this.concat(obj.toString());
   }
 
   String substring(int startIndex, [int endIndex = null]) {
     if (endIndex == null) endIndex = this.length;
 
     if ((startIndex < 0) || (startIndex > this.length)) {
       throw new IndexOutOfRangeException(startIndex);
     }
     if ((endIndex < 0) || (endIndex > this.length)) {
       throw new IndexOutOfRangeException(endIndex);
     }
     if (startIndex > endIndex) {
       throw new IndexOutOfRangeException(startIndex);
     }
     return _substringUnchecked(startIndex, endIndex);
   }
 
   String trim() native;
 
-  bool contains(Pattern pattern, int startIndex) {
-    if (startIndex == null) startIndex = 0;
+  bool contains(Pattern pattern, [int startIndex = 0]) {
     if (startIndex < 0 || startIndex > length) {
       throw new IndexOutOfRangeException(startIndex);
     }
     if (pattern is String) {
       return this.indexOf(pattern, startIndex) != -1;
     } else if (pattern is JSSyntaxRegExp) {
       JSSyntaxRegExp regExp = pattern;
       return regExp.hasMatch(_substringUnchecked(startIndex, length));
     } else {
       String substr = _substringUnchecked(startIndex, length);
@@ skipping 126 matching lines @@
     for (int g in groups) {
       result.add(group(g));
     }
     return result;
   }
 
   final int _start;
   final String str;
   final String pattern;
 }