Remove Document::m_closeAfterStyleRecalc and the associated code

This code was introduced at the dawn of time 8 years ago to fix a bug where we
let plugins load inside ::attach and they could cause us to call implicitClose
too early: https://trac.webkit.org/changeset/9126

We've long since stopped loading the plugins inside the ::attach call instead
using the PostAttachCallback list so this code can never run anyway, in fact
even the test for this code was deleted long ago in
https://trac.webkit.org/changeset/63563

Review URL: https://chromiumcodereview.appspot.com/23201003

git-svn-id: svn://svn.chromium.org/blink/trunk@156138 bbb929c8-8fbe-4397-9dbb-9b2b20218538