To reproduce: 1. Go to https://bugs.webkit.org/ 2. Type something in the search field near the bottom of the page 3. Press Enter The form is not submitted. I'm pretty sure this used to work in WebKit2, and it definitely works in WebKit1.
<rdar://problem/8695027>
Spy++ shows that WebKit1 gets WM_KEYDOWN/WM_CHAR/WM_KEYUP, while WebKit2 only gets WM_KEYDOWN/WM_KEYUP.
Looks like this is an issue in Safari, not WebKit.