Allow hybrid elements (like iron-list) to make template instances wit…

…h mutable data

lib/legacy/legacy-element-mixin.html

@@ -15,6 +15,7 @@
 <link rel="import" href="../utils/import-href.html">
 <link rel="import" href="../utils/render-status.html">
 <link rel="import" href="../utils/unresolved.html">
+<link rel="import" href="mutable-data-behavior.html">
 <link rel="import" href="polymer.dom.html">
 
 <script>

lib/legacy/templatizer-behavior.html

@@ -84,11 +84,15 @@
        * by `stamp` to create new instances of the template.
        *
        * @param {HTMLTemplateElement} template Template to prepare
+       * @param {Boolean=} mutableData When `true`, the generated class will skip
+       *   strict dirty-checking for objects and arrays (always consider them to
+       *   be "dirty"). Defaults to false.
        * @return {TemplateInstance} Description
        */
-      templatize(template) {
+      templatize(template, mutableData) {
         this._templatizerTemplate = template;
         this.ctor = Polymer.Templatize.templatize(template, this, {
+          mutableData: Boolean(mutableData),
           parentModel: this._parentModel,
           instanceProps: this._instanceProps,
           forwardHostProp: this._forwardHostPropV2,

lib/utils/templatize.html

@@ -354,6 +354,9 @@
        *   to the instance by the templatize owner.  These properties shadow any
        *   host properties, and changes within the template to these properties
        *   will result in `notifyInstanceProperties` to be called.
+       * - `mutableData`: When `true`, the generated class will skip strict
+       *   dirty-checking for objects and arrays (always consider them to be
+       *   "dirty").
        * - `notifyInstanceProperties(instance, property, value)`: Called when
        *   an instance property changes.  Users may choose to call `notifyPath`
        *   on e.g. the owner to notify the change.