Fix detached callback and add isAttached to SkyElements.

sky/tests/framework/templates.sky

Index: sky/tests/framework/templates.sky
diff --git a/sky/tests/framework/templates.sky b/sky/tests/framework/templates.sky
index 30e119fc41245eef95441152d2515a3c1a8106b2..2ad0674c663fb05b4b8bf660ab70bad66396a337 100644
--- a/sky/tests/framework/templates.sky
+++ b/sky/tests/framework/templates.sky
@@ -17,6 +17,14 @@ describe("SkyElement templates", function() {
     element.remove();
   });
 
+  it("should update isAttached when inserting", function() {
+    assert.isFalse(element.isAttached);
+    sandbox.appendChild(element);
+    assert.isTrue(element.isAttached);
+    element.remove();
+    assert.isFalse(element.isAttached);
+  });
+
   it("should stamp when the element is inserted", function() {
     assert.isNull(element.shadowRoot);
     sandbox.appendChild(element);