Only show quit instruction bubble on browser windows

The new instruction bubble's recommendation to "press Alt+F" won't work on
non-browser windows, so don't show the instructions unless the focused window is
a browser window and has a toolbar.

BUG=243164
R=sky

Change-Id: I1ab550ff57134009a2cbb0a1ee612775c1323e88
Reviewed-on: https://chromium-review.googlesource.com/1197343
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#587787}
1 file changed