This may be an old thread, but as it's the top hit on google I thought I'd make someone's life easy :).  Having found no way to do shift+enter for I'm feeling lucky, I wrote an autohotkey script using anony1's answer and "l" as the hotkey (instead of <).  If you don't know how to use autohotkey I suggest looking it up, its awesome :D

This can just be pasted into a script -

#IfWinActive Chrome
+Enter::
{
CoordMode, Mouse, Relative
MouseGetPos,, ypos
If ypos<69
{
ClipboardOld = %ClipboardAll%
Clipboard =  ;
Send ^a
Send ^x
Send l{Space}
Send ^v
Send {Enter}
Clipboard = %ClipboardOld%
}
else
Send +{Enter}
}