MobileFrontend extension is currently tracking watched/temp-watch
css classes and applying animations to the "watch" event.
This patch starts adding temp-watched accordingly now that the
expiry is part of the event's data.
Note: this patch does not fix the lack of animation when transitioning
from half-star to empty-star or on page-load when the page is
temporarily watched but it fixes the awkward angle the half-star
icon was left in when transitioning from a full-star to a half-star
Bug: T262862
Change-Id: I1c8cb9c33cda76b87b6a9f15e408d88edbf61d93
