Remove dead code from HTMLViewSourceDocument

There's no reason to call lazyAttach() anymore after calling parserAppendChild.
This patch also removes some code that doesn't compile behind an ifdef which
uses an API that no longer exists (ContainerNode::addChild?) which was also
calling lazyAttach.

Review URL: https://codereview.chromium.org/55083003

git-svn-id: svn://svn.chromium.org/blink/trunk@161081 bbb929c8-8fbe-4397-9dbb-9b2b20218538