R1:19d0d2808984

Use keyboard shortcuts for the "`" darkconsole toggle.

Summary:
This simplifies it a lot and prevents it from spazzing out when some control is
foucsed.

Test Plan:
Hit "?", "`".

Reviewed By: aran
Reviewers: jungejason, aran, tuomaspelkonen
CC: aran
Differential Revision: 410