Implement getRange (returning an Iterable).

runtime/lib/growable_array.dart

Index: runtime/lib/growable_array.dart
diff --git a/runtime/lib/growable_array.dart b/runtime/lib/growable_array.dart
index ba0b90a16db6c22dc5f561cba632a1bef4ed6b1c..0714fb771534a8b11017e45dd992f992bfa0468a 100644
--- a/runtime/lib/growable_array.dart
+++ b/runtime/lib/growable_array.dart
@@ -69,6 +69,10 @@ class _GrowableObjectArray<T> implements List<T> {
                                             (T element) => !test(element));
   }
 
+  Iterable<T> getRange(int start, int end) {
+    return IterableMixinWorkaround.getRangeList(this, start, end);
+  }
+
   void setRange(int start, int length, List<T> from, [int startFrom = 0]) {
     IterableMixinWorkaround.setRangeList(this, start, length, from, startFrom);
   }
@@ -119,8 +123,6 @@ class _GrowableObjectArray<T> implements List<T> {
     return list;
   }
 
-  List<T> getRange(int start, int length) => sublist(start, start + length);
-
   factory _GrowableObjectArray(int length) {
     var data = new _ObjectArray((length == 0) ? 4 : length);
     var result = new _GrowableObjectArray<T>.withData(data);