When the return key is pressed, we try to handle it as a commit action
for input elements. However, we would then go on to actually insert the
return key's code point (U+000D) into the input element. This would be
sanitized out, but would leave the input element in a state where it
thinks it has text to commit. This would result in a change event being
fired when the return key is pressed multiple times in a row.
We were also firing the beforeinput/input events twice for all return
key presses.
To fix this, this patch changes the input event target to signify if it
actually handled the return key. If not (i.e. for textarea elements),
only then do we insert the code point. We also must not fall through to
the generic key handler, to avoid the repeated input events.
We currently fire the change event on <input> elements when they lose
focus. The spec allows for us to also fire the event when changes are
"committed", so long as such an action makes sense for the input type.
This patch detects when the return key is entered in an <input> element
and uses that as the commit action for text-related types. If no change
has occurred since the last commit, no change event is fired.
