Convert more MarkOnlyThis calls to use SubtreeLayoutScope.

This is part of the larger project of getting rid of MarkOnlyThis entirely
so we have better assurances that parts of the subtree don't get left
unlayouted.

Also, remove MarkContainingBlockChain arguments in a couple places.
It's the default, so no need to pass it in.

Finally, change forceChildLayout to call layout instead of forceLayout.
Calling forceLayout was just an accident. No need to setNeedsLayout.

Review URL: https://chromiumcodereview.appspot.com/22934005

git-svn-id: svn://svn.chromium.org/blink/trunk@156167 bbb929c8-8fbe-4397-9dbb-9b2b20218538