Revert 168061 "Revert 168053 "Fix a crash when spell checker is ..."

Did not seem to fix crashes.

> Revert 168053 "Fix a crash when spell checker is triggered for a..."
> 
> May have caused crashes on Android bot.
> 
> > Fix a crash when spell checker is triggered for an editable element which is in an author ShadowRoot of an INPUT element.
> > 
> > enclosingTextFormControl() should handle only elements in UA ShadowRoot.
> > 
> > BUG=343040
> > TEST=automated
> > 
> > Review URL: https://codereview.chromium.org/181273002
> 
> TBR=tkent@chromium.org
> 
> Review URL: https://codereview.chromium.org/183793005

TBR=pkasting@chromium.org



git-svn-id: svn://svn.chromium.org/blink/trunk@168075 bbb929c8-8fbe-4397-9dbb-9b2b20218538