Move call to didRecalculateStyleForElement into styleForRenderer

styleForRenderer() is really what does the computation of the style for
an element so we should put the counter there. This also removes the
code duplication between ::recalcOwnStyle and ::attach.

Review URL: https://codereview.chromium.org/263993003

git-svn-id: svn://svn.chromium.org/blink/trunk@173260 bbb929c8-8fbe-4397-9dbb-9b2b20218538