Intentionally bloat RenderObject

This has been talked about for years that we should never
grow RenderObject or else we would regress performance. We
have enough coverage to catch and quantify any performance
hit so let's land this and rock 'n' roll.

Review URL: https://codereview.chromium.org/35333003

git-svn-id: svn://svn.chromium.org/blink/trunk@160402 bbb929c8-8fbe-4397-9dbb-9b2b20218538