Fix edit | edit source link tabbing in Firefox

When you selected the "edit" link by tabbing, the links would expand.
In Chrome, you could then tab to the "edit source" link, but in Firefox,
the links would just contract back and you couldn't reach "edit source".

This happened because in Chrome, the "edit source" link is already
considered to be focused when the blur event happens on the "edit" link.
But in Firefox, this is not the case: the blur fires first, and only
after that does Firefox determine what to focus next.

Fixed by waiting 100ms to contract after blur, just like we do on
mouseleave.

Change-Id: I9a38b629ca5e580003d82a3dca8dbf7564486fa0
Merge "Fix edit | edit source link tabbing in Firefox"