Create generic check methods for RangeError causing checks.

sdk/lib/internal/list.dart

 // Copyright (c) 2013, 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.
 
 part of dart._internal;
 
 /**
  * Mixin that throws on the length changing operations of [List].
  *
  * Intended to mix-in on top of [ListMixin] for fixed-length lists.
@@ skipping 220 matching lines @@
 abstract class UnmodifiableListBase<E> =
     ListBase<E> with UnmodifiableListMixin<E>;
 
 class _ListIndicesIterable extends ListIterable<int> {
   List _backedList;
 
   _ListIndicesIterable(this._backedList);
 
   int get length => _backedList.length;
   int elementAt(int index) {
-    if (index < 0 || index >= length) {
-      throw new RangeError.index(index, this);
-    }
+    RangeError.checkValidIndex(index, this);
     return index;
   }
 }
 
 class ListMapView<E> implements Map<int, E> {
   List<E> _values;
 
   ListMapView(this._values);
 
   E operator[] (int key) => containsKey(key) ? _values[key] : null;
@@ skipping 115 matching lines @@
  * or become empty or been otherwise modified.
  * It will still be a valid object, so references to it will not, e.g., crash
  * the runtime if accessed, but no promises are made wrt. its contents.
  *
  * This unspecified behavior is the reason the function is not exposed to
  * users. We allow the underlying implementation to make the most efficient
  * conversion, at the cost of leaving the original list in an unspecified
  * state.
  */
 external List makeListFixedLength(List growableList);