Make List.from and Iterable.toList default to not growable.

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 0c0658b7ed6e58b32d31a74f27f414c280955637..2c289ef5ae7395f9980185739a15ed1f72709df2 100644
--- a/tools/dom/templates/immutable_list_mixin.darttemplate
+++ b/tools/dom/templates/immutable_list_mixin.darttemplate
@@ -42,7 +42,7 @@ $endif
 
   bool any(bool f($E element)) => IterableMixinWorkaround.any(this, f);
 
-  List<$E> toList({ bool growable: false }) =>
+  List<$E> toList({ bool growable: true }) =>
       new List<$E>.from(this, growable: growable);
 
   Set<$E> toSet() => new Set<$E>.from(this);