Document should not use confusingAndOftenMisusedAttached()

Switch all the callers of confusingAndOftenMisusedAttached() in Document.cpp
to something more specific. I tried this once, but I changed too many things
in the same patch like changing the nulling out of the RenderView inside
Document::detach: https://codereview.chromium.org/26347002

This patch changes fewer things and only switches the callers inside
Document.cpp. Future patches will attempt to clean up Documen::detach
like I did in the original patch.

Review URL: https://codereview.chromium.org/54233004

git-svn-id: svn://svn.chromium.org/blink/trunk@161087 bbb929c8-8fbe-4397-9dbb-9b2b20218538