innerHTML (innerText and textContent) should lazyAttach

Just like doing appendChild() to add children, innerHTML should use
lazyAttach.

This leaves editing and the parser as the last users of synchronous
attach.

BUG=230268

Review URL: https://chromiumcodereview.appspot.com/22917003

git-svn-id: svn://svn.chromium.org/blink/trunk@156076 bbb929c8-8fbe-4397-9dbb-9b2b20218538