To reproduce this bug, navigate to the Bing homepage or a Bing search results page, type something in the Bing search field, and press return. Nothing happens.
This is the regression range: <http://trac.webkit.org/log/trunk/?rev=166621&stop_rev=166612>. I strongly suspect <http://trac.webkit.org/r166615>, the fix for bug 131055.
Confirmed that this was caused by r166615.
Created attachment 228607 [details]
Created attachment 228608 [details]
Let's not a revert a FIXME.