add hacky call-out for custom element to upgrade during instance crea…

…tion (cloneNode)

BUG=

Review URL: https://codereview.appspot.com/8291043

src/template_element.js

@@ -294,7 +294,13 @@
 
   function createInstance(element, model, delegate) {
     var content = element.ref ? element.ref.content : element.content;
-    return createDeepCloneAndDecorateTemplates(content);
+    var instance = createDeepCloneAndDecorateTemplates(content);
+    // TODO(rafaelw): This is a hack, and is neccesary for the polyfil
+    // because custom elements are not upgraded during cloneNode()
+    if (typeof HTMLTemplateElement.__instanceCreated == 'function') {
+      HTMLTemplateElement.__instanceCreated(instance);
+    }
+    return instance;
   }
 
   mixin(HTMLTemplateElement.prototype, {

tests/template_element.js

@@ -1429,4 +1429,21 @@ suite('Template Element', function() {
     assert.strictEqual(1, template3.content.childNodes.length);
     assert.strictEqual('Hello', template3.content.firstChild.textContent);
   });
+
+  test('__instanceCreated() hack', function() {
+    var called = false;
+    HTMLTemplateElement.__instanceCreated = function(node) {
+      assert.strictEqual(Node.DOCUMENT_FRAGMENT_NODE, node.nodeType);
+      called = true;
+    }
+
+    var div = createTestHtml('<template bind="{{}}">Foo</template>');
+    assert.isFalse(called);
+
+    HTMLTemplateElement.bindTree(div);
+    Model.notifyChanges();
+    assert.isTrue(called);
+
+    HTMLTemplateElement.__instanceCreated = undefined;
+  });
 });