Add tests for Element#elements.

client/html/src/_Lists.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.
-
-// TODO(jacobr): move into a core library or at least merge with the copy
-// in client/dom/src
-class _Lists {
-
-  /**
-   * Returns the index in the array [a] of the given [element], starting
-   * the search at index [startIndex] to [endIndex] (exclusive).
-   * Returns -1 if [element] is not found.
-   */
-  static int indexOf(List a,
-                     Object element,
-                     int startIndex,
-                     int endIndex) {
-    if (startIndex >= a.length) {
-      return -1;
-    }
-    if (startIndex < 0) {
-      startIndex = 0;
-    }
-    for (int i = startIndex; i < endIndex; i++) {
-      if (a[i] == element) {
-        return i;
-      }
-    }
-    return -1;
-  }
-
-  /**
-   * Returns the last index in the array [a] of the given [element], starting
-   * the search at index [startIndex] to 0.
-   * Returns -1 if [element] is not found.
-   */
-  static int lastIndexOf(List a, Object element, int startIndex) {
-    if (startIndex < 0) {
-      return -1;
-    }
-    if (startIndex >= a.length) {
-      startIndex = a.length - 1;
-    }
-    for (int i = startIndex; i >= 0; i--) {
-      if (a[i] == element) {
-        return i;
-      }
-    }
-    return -1;
-  }
-}