Add shadowRootReady callback for SkyElement.

sky/tests/framework/templates.sky

 <sky>
 <import src="/sky/tests//resources/chai.sky" />
 <import src="/sky/tests/resources/mocha.sky" />
 <import src="/sky/tests/resources/test-element.sky" as="TestElement" />
 
 <div id="sandbox"></div>
 
 <script>
 describe("SkyElement templates", function() {
   var element;
@@ skipping 31 matching lines @@
 
   it("should connect event handlers", function() {
     sandbox.appendChild(element);
     var inside = element.shadowRoot.getElementById("inside");
     inside.dispatchEvent(new CustomEvent("wrong-event"));
     assert.isNull(element.lastEvent);
     var event = new CustomEvent("test-event");
     inside.dispatchEvent(event);
     assert.equal(element.lastEvent, event);
   });
+
+  it("should call shadowRootReady after creating the template instance", function() {
+    assert.equal(element.shadowRootReadyCount, 0);
+    sandbox.appendChild(element);
+    assert.equal(element.shadowRootReadyCount, 1);
+    element.remove();
+    sandbox.appendChild(element);
+    assert.equal(element.shadowRootReadyCount, 1);
+  });
 });
 </script>
 </sky>