VM: Remove _GrowableList.from which was never called.

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 016a4543aa0aaf5b242a030ab6fc606f14c348e0..271c71a12264d2c0928dbe82dc9a3ef853725ec1 100644
--- a/runtime/lib/growable_array.dart
+++ b/runtime/lib/growable_array.dart
@@ -104,12 +104,6 @@ class _GrowableList<T> extends ListBase<T> {
     return new _GrowableList<T>.withData(data);
   }
 
-  factory _GrowableList.from(Iterable<T> other) {
-    List<T> result = new _GrowableList<T>();
-    result.addAll(other);
-    return result;
-  }
-
   factory _GrowableList.withData(_List data)
     native "GrowableList_allocate";