Change getRange to sublist. Make getRange deprecated.

tools/dom/templates/immutable_list_mixin.darttemplate

Index: tools/dom/templates/immutable_list_mixin.darttemplate
diff --git a/tools/dom/templates/immutable_list_mixin.darttemplate b/tools/dom/templates/immutable_list_mixin.darttemplate
index 598fde2fded9eb6429a26642ffc5d5e82f3ba97d..11aed324df9b08185954f5a03f19aaafa533cd23 100644
--- a/tools/dom/templates/immutable_list_mixin.darttemplate
+++ b/tools/dom/templates/immutable_list_mixin.darttemplate
@@ -188,8 +188,13 @@ $endif
     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);