Workaround for #10124: change the title on close.

On Mac/OSX alert causes system modal dialog which prevents any interaction with
the browser and navigating away. This was causing unit tests to fail.

So instead of showing alert, change the title of the document to indicate that
the Live Preview session was closed. A more clear UI/UX definition is needed
for definitive solution.
Address review comments.

    - Exclude failing test.
    - Add full screen overlay on Live Preview close in browser.
Merge pull request #10129 from adobe/kai/fix-mb-livedev-test-failures

Workaround for #10124: change the title on close.
Revert changes for terminating Tern worker on quit.
Merge pull request #10135 from adobe/rlim/revert-worker-termination

Revert changes for terminating Tern worker on quit.