Revert 177853 "HTML Imports: Let root state recalculation delay"

> HTML Imports: Let root state recalculation delay
> 
> It has a race which hits an ASSERT().
> This change makes it delayed to run it in its own call stack.
> 
> BUG=390176
> TEST=import-insert-domcontnetloaded.html
> R=dglazkov@chromium.org, dominicc@chromium.org
> 
> Review URL: https://codereview.chromium.org/368743002

Reason for revert: Causes crash in layout test
fast/html/imports/import-insert-domcontentloaded.html

TBR=morrita@chromium.org

Review URL: https://codereview.chromium.org/385703002

git-svn-id: svn://svn.chromium.org/blink/trunk@177864 bbb929c8-8fbe-4397-9dbb-9b2b20218538