Counter shouldn't invalidate the tree in the middle of layout

This change remove the counter-invalidation-during-layout-madness
by moving the invalidation just before layout in FrameView. This
removes the need to weaken one of our layout ASSERTs.

BUG=267196

Review URL: https://chromiumcodereview.appspot.com/23190043

git-svn-id: svn://svn.chromium.org/blink/trunk@157155 bbb929c8-8fbe-4397-9dbb-9b2b20218538