Add "growable" parameter to List.filled constructor.

runtime/lib/array_patch.dart

Index: runtime/lib/array_patch.dart
diff --git a/runtime/lib/array_patch.dart b/runtime/lib/array_patch.dart
index abe5a193d4aaa9eec261487476bef350ee05b875..c0ddfeec1c35bdde3963c3b31b4d8107b0650c84 100644
--- a/runtime/lib/array_patch.dart
+++ b/runtime/lib/array_patch.dart
@@ -20,10 +20,10 @@ patch class List<E> {
     return new _List<E>(length);
   }
 
-  /* patch */ factory List.filled(int length, E fill) {
+  /* patch */ factory List.filled(int length, E fill, {bool growable: false}) {
     // All error handling on the length parameter is done at the implementation
     // of new _List.
-    var result = new _List<E>(length);
+    var result = growable ? new _GrowableList<E>(length) : new _List<E>(length);
     if (fill != null) {
       for (int i = 0; i < length; i++) {
         result[i] = fill;