Change getRange to sublist. Make getRange deprecated.

tools/dom/templates/immutable_list_mixin.darttemplate

   // -- start List<$E> mixins.
   // $E is the element type.
 
   // From Iterable<$E>:
 
   Iterator<$E> get iterator {
     // Note: NodeLists are not fixed size. And most probably length shouldn't
     // be cached in both iterator _and_ forEach method. For now caching it
     // for consistency.
     return new FixedSizeListIterator<$E>(this);
@@ skipping 166 matching lines @@
   }
 
   void removeRange(int start, int rangeLength) {
     throw new UnsupportedError("Cannot removeRange on immutable List.");
   }
 
   void insertRange(int start, int rangeLength, [$E initialValue]) {
     throw new UnsupportedError("Cannot insertRange on immutable List.");
   }
 
+  List<$E> sublist(int start, [int end]) {
+    if (end == null) end = length;
+    return Lists.getRange(this, start, end, <$E>[]);
+  }
+
   List<$E> getRange(int start, int rangeLength) =>
-      Lists.getRange(this, start, rangeLength, <$E>[]);
+      sublist(start, start + rangeLength);
 
   Map<int, $E> asMap() =>
     IterableMixinWorkaround.asMapList(this);
 
   // -- end List<$E> mixins.