Implement List.getRange.

runtime/lib/arrays.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.
 
 class Arrays {
 
   static String asString(Array array) {
     String result = "[";
     int len = array.length;
     for (int i = 0; i < len; i++) {
@@ skipping 68 matching lines @@
     if (startIndex >= a.length) {
       startIndex = a.length - 1;
     }
     for (int i = startIndex; i >= 0; i--) {
       if (a[i] == element) {
         return i;
       }
     }
     return -1;
   }
+
+  static void rangeCheck(Array a, int start, int length) {
+    if (length < 0) {
+      throw new IllegalArgumentException("negative length $length");
+    }
+    if (start < 0 || start > a.length) {
+      throw new IndexOutOfRangeException(start);
+    }
+    if (start + length > a.length) {
+      throw new IndexOutOfRangeException(start + length);
+    }
+  }
 }