Revert of Unfocused TEXTAREA element should not accept editing. (https://codereview.chromium.org/246073004/)

Reason for revert:
Broke editing/selection/4960116.html on Mac and Linux32.


Original issue's description:
> Unfocused TEXTAREA element should not accept editing.
> 
> The normal unfocusing step clears selection. But unfocusing caused by
> display:none style didn't clear selection because:
>  - It used Document::setFocusedElement. It bypassed FocusController.
>  - Even if it used it, clearSelectionIfNeeded() in FocusController didn't
>     clear selection because selection.rootEditableElement() was null in
>     this case.
> 
> This CL changes the code so that:
>  - We use Element::blur(), which uses FocusController::setFocusedElement.
>  - clearSelectionIfNeeded() uses enclosingTextFormControl() to check
>     if the selection is in INPUT/TEXTAREA instead of
>     rootEditableElement(), which depends on renderers.
> 
> BUG=364309
> TEST=automated
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=172121

TBR=yosin@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=364309

Review URL: https://codereview.chromium.org/248433002

git-svn-id: svn://svn.chromium.org/blink/trunk@172241 bbb929c8-8fbe-4397-9dbb-9b2b20218538