Previously any message reaching the widget closed the Sign In dropdown,
because the handler returned early only for a clickOutside payload while
closing was disabled and fell through to closing in every other case. The
embedding page posts hash, title and theme messages of its own, and
`embed.ts` installs a MutationObserver on the host page title that posts on
every mutation, so a host page whose title changes closes an open login form
and discards whatever was typed into it. Browser extensions that post into
the page have the same effect.
After this change the dropdown closes only for a clickOutside payload from
`window.parent`. Reproduced against the deployed demo: with the form open and
filled, a single `document.title` assignment on the host page removed it,
while three seconds of inactivity did not.
Resolves#2139.
Dmitry VerkhoturovandUmputun
8bcfd9e456