Tests that stepping into custom element methods will lead to a pause in the callbacks.

Set timer for test function.
Stepping to constructor...
Stepping into constructor...
PASS: Did step into event listener(FooElement).
Stepping to setAttribute...
Stepping into setAttribute...
PASS: Did step into event listener(attributeChangedCallback).
Stepping to connectedCallback...
Stepping into connectedCallback...
PASS: Did step into event listener(connectedCallback).
Stepping to disconnectedCallback...
Stepping into disconnectedCallback...
PASS: Did step into event listener(disconnectedCallback).
[page] Invoked constructor.
[page] Invoked attributeChangedCallback.
[page] Invoked connectedCallback.
[page] Invoked disconnectedCallback.