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 bdaaaf8ba7aa98e23e66d69c1fe236c23797edf1..64912547c2e18c1aa65c87ca8a28f3566226ae55 100644
--- a/tools/dom/templates/immutable_list_mixin.darttemplate
+++ b/tools/dom/templates/immutable_list_mixin.darttemplate
@@ -184,8 +184,13 @@ $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);