Confirm-to-quit: Fix missing Ctrl+Shift+Q keyup event when omnibox is focused

Also clean up some event routing to ConfirmQuitBubbleController.

BUG=243164
R=sky

Change-Id: I2dfeb60c6efb24816b73db3f0e014a0deb648be5
Reviewed-on: https://chromium-review.googlesource.com/1104884
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568887}
8 files changed