RenderCounter should not use confusingAndOftenMisusedAttached()

It's not entirely clear what this code is doing, but it looks like it
wants needsAttach() to avoid doing work when you know the node is not
yet done attaching.

Review URL: https://codereview.chromium.org/53803003

git-svn-id: svn://svn.chromium.org/blink/trunk@161038 bbb929c8-8fbe-4397-9dbb-9b2b20218538