In the timeline's activity graph, hit testing is broken after a window resize

STR:

1. open a profile like [this one](https://profiler.firefox.com/public/z7jpz18p7e9j778mr0bccaj7nrejspqcxcbe1hg/calltree/?globalTrackOrder=0-1-2-3-4-5-6-7-8-9-10-11-12&hiddenGlobalTracks=0-1-2-3-4-5-6-7-8-9-10-11&hiddenLocalTracksByPid=12209-0&localTrackOrderByPid=12111-51-52-0-1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18-19-20-21-22-23-24-25-26-27-28-29-30-31-32-33-34-35-36-37-38-39-40-41-42-43-44-45-46-47-48-49-50~12638-0~12150-0~12500-0~12440-0~12257-0~12286-0~12270-0~12265-0-1~12261-0-1~12254-0-1~12279-0~12209-0~&thread=63&timelineType=cpu-category&v=5)
1. resize the window (for example by opening devtools on the right)

=> see how hit testing reacts weirdly

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-393)