StyleResolverParentPusher can decide if it needs to push at creation time

We can decide at creation time if the ParentPusher needs to push a parent
style to the bloom filter instead of having a push() method call inside
of each of the loops during recalcStyle.

I also removed the ASSERT and if statement (with the same check) from inside
the ParentPusher. There's no reason to guard against getting the parent stack
wrong, the stack itself already has guards against it and getting it wrong is
not a security issue (so there's no reason for an ASSERT and duplicate if).

Review URL: https://codereview.chromium.org/68253003

git-svn-id: svn://svn.chromium.org/blink/trunk@161770 bbb929c8-8fbe-4397-9dbb-9b2b20218538