Early return in markContainingBlocksForLayout if selfNeedsLayout.

This is just a performance optimization. This will be useful as we get rid
of setNeedsLayout(MarkOnlyThis) calls.

Review URL: https://chromiumcodereview.appspot.com/21142005

git-svn-id: svn://svn.chromium.org/blink/trunk@155212 bbb929c8-8fbe-4397-9dbb-9b2b20218538