Revert "Have Node::document() return a reference instead of a pointer"

This reverts commit deb25381d69b6bed38d488b37e2325c3905624c1.

BUG=none
TBR=ch.dumez@sisa.samsung.com

Review URL: https://codereview.chromium.org/23567008

git-svn-id: svn://svn.chromium.org/blink/trunk@157021 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Auto-rebaseline for r157008

http://src.chromium.org/viewvc/blink?view=revision&revision=157008

TBR=fmalita@chromium.org

Review URL: https://codereview.chromium.org/23530011

git-svn-id: svn://svn.chromium.org/blink/trunk@157022 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Have Node::document() return a reference instead of a pointer

Have Node::document() return a reference instead of a pointer now that the
method can no longer return NULL. DocumentType Nodes have been recently
updated so that they always have an associated document (as per DOM4).

R=abarth@chromium.org
BUG=281400

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=157019

Review URL: https://codereview.chromium.org/23819007

git-svn-id: svn://svn.chromium.org/blink/trunk@157023 bbb929c8-8fbe-4397-9dbb-9b2b20218538