[LayoutNG] Fix positioning of zero-block-size-div, and content size.
This patch does a few small things:
- Removes adding the end margin for a zero-block-size-div for positioning
(which was incorrect).
- Calculate the final content_size_ based off the previous inflow position.
(If it was -ve, we'd overestimate the height).
- Clarified a few comments.
BUG=635619
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Review-Url: https://codereview.chromium.org/2954013002
Cr-Commit-Position: refs/heads/master@{#482017}
4 files changed
