[LayoutNG] Empty block clearing should contribute to content size.

A pretty simple fix, this just makes sure we adjust our size if an empty block
cleared something.

Bug: 635619
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Change-Id: Iae53ae7eec7818756490bedeb25cac4ef3d9d53c
Reviewed-on: https://chromium-review.googlesource.com/603719
Commit-Queue: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#492545}
3 files changed