Called by the DOM when this element has been inserted into the live document.
More information can be found in the Custom Elements draft specification.
void attached() {
if (!_elementPrepared) {
// Dart specific message for a common issue.
throw new StateError('polymerCreated was not called for custom element '
'$_name, this should normally be done in the .created() if Polymer '
'is used as a mixin.');
}
cancelUnbindAll();
if (!hasBeenAttached) {
_hasBeenAttached = true;
async((_) => domReady());
}
}