Not all our errors actually happen in the contexts we were
wrapping (e.g. `setTimeout` and `_.throttle`). Also this fixes the
neat Firefox inspector feature that shows you where your event
handlers for a given DOM element actually live.
Using this "semi-modern" browser event means that Safari 9 and older
and IE10 and older may not have our browser error reporting active;
that seems fine giving the vanishing market share of those browsers.
https://blog.sentry.io/2016/01/04/client-javascript-reporting-window-onerror
Signed-off-by: Anders Kaseorg <anders@zulipchat.com>
This run_test helper sets up a convention that allows
us to give really short tracebacks for errors, and
eventually we can have more control over running
individual tests. (The latter goal has some
complications, since we often intentionally leak
setup in tests.)