Revert 159803 "Revert 159188 "Document should not use confusingA..."

> Revert 159188 "Document should not use confusingAndOftenMisusedA..."
> 
> This change is likely the cause of crbug.com/306566 (our top
> crasher). Unfortunately nobody can repro this bug so this is
> an optimistic revert.
> 
> > Document should not use confusingAndOftenMisusedAttached()
> > 
> > Switch all uses in Document.cpp of confusingAndOftenMisusedAttached()
> > to use the new DocumentLifecycle concept. This also switched away from
> > nulling out the RenderView on Document to indicate "destruction mode",
> > and now uses the Stopping state of Document which is much nicer and
> > means the render tree still has access to the root of the tree even
> > during teardown.
> > 
> > R=abarth@chromium.org
> > 
> > Review URL: https://codereview.chromium.org/26347002
> 
> TBR=esprehn@chromium.org
> 
> Review URL: https://codereview.chromium.org/27509004

TBR=jchaffraix@chromium.org

Review URL: https://codereview.chromium.org/27549003

git-svn-id: svn://svn.chromium.org/blink/trunk@159804 bbb929c8-8fbe-4397-9dbb-9b2b20218538