Remove insertRange.

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 357d89e8be64fe441af8d2d293cbff1e0f468d4e..ae81f68e0bcbc2cc04ac867b80635bf268596584 100644
--- a/tools/dom/templates/immutable_list_mixin.darttemplate
+++ b/tools/dom/templates/immutable_list_mixin.darttemplate
@@ -167,14 +167,10 @@ $endif
     throw new UnsupportedError("Cannot setRange on immutable List.");
   }
 
-  void removeRange(int start, int rangeLength) {
+  void removeRange(int start, int end) {
     throw new UnsupportedError("Cannot removeRange on immutable List.");
   }
 
-  void insertRange(int start, int rangeLength, [$E initialValue]) {
-    throw new UnsupportedError("Cannot insertRange on immutable List.");
-  }
-
   Iterable<$E> getRange(int start, int end) =>
     IterableMixinWorkaround.getRangeList(this, start, end);