If the profiler hangs when capturing a profile, it's easy to hit the shortcut multiple times to ensure it's opening. The problem is that then multiple tabs are opened and attempt to load the profile. This can lead to errors, and getting the profiler into a bad state.

We should make sure that the shortcuts don't send a bunch of duplicate commands through when hanging. For instance:

Steps to reproduce:

• CtrlShift+1
• Do something in the browser
• CtrlShift+2
• Hang
• CtrlShift+2
• CtrlShift+2

Expected results:

Only one tab should open with the profile

Actual results:

Multiple tabs open, and throw errors from all trying to load the profile.

On linux, there's also a hang when starting the profile, and it's very common that a press the shortcut to start twice -- as as result it stops right away :-)

If we implement an immediate visual feedback this will help too. (I think we have a separate bug for this already)

This patch handles the issue where a user sends two commands two toggle the profiler and/or
capture. This gets the profiler UI in a weird state that usually is just because the UI
is hanging and lagging. This makes the profiler pause state into a "capturing" state.
I did not include a test with the behavior change, as I was worried about intermittent
failures on asserting this behavior.

Depends on D75849

https://hg.mozilla.org/mozilla-central/rev/147bf269db00