By adding a way to wait a short time for a component to appear in
the DOM, so we don't get flakey failures like this when we change
something to returning a promise that needs to resolve before the
component actually appears.
It seems that a number of the tests had started failing when run in
Chrome. They were fine under PhantomJS, but the MegolmExport tests only work
under Chrome, and I need them to work...
Mostly the problems were timing-related, where assumptions made about how
quickly the `then` handler on a promise would be called were no longer
valid. Possibly Chrome 55 has made some changes to the relative priorities of
setTimeout and sendMessage calls.
One of the TimelinePanel tests was failing because it was expecting the contents
of a div to take up more room than they actually were. It's possible this is
something very environment-specific; hopefully the new value will work on a
wider range of machines.
Also some logging tweaks.
It turns out that a bunch of things rely on MatrixClient methods to return
promises rather than undefined. Rather than having to undo half the work done
by sinon.createStubInstance, just build our own object with as many methods as
we need stubbed out.
Under certain conditions, it was possible to get stuck in a state where any
user-initiated scroll would be met with "Working around
vector-im/vector-web#528" and overridden. Fix this by removing the duplication
between _lastSetScroll and recentEventScroll, and using _lastSetScroll which is
more reliable.
David Baker