Clean up the initializer mess in Document.

Before this, some members were initialized in the initializer list and
others were initialized in the body of the constructor. As far as I can
tell, it's OK for everything to just be in the initializer list.

As a bonus, I found two completely unused members in Document (and a
local static) and removed them as well.

Review URL: https://chromiumcodereview.appspot.com/16276002

git-svn-id: svn://svn.chromium.org/blink/trunk@151593 bbb929c8-8fbe-4397-9dbb-9b2b20218538
2 files changed