[layout-ng] Use correct height for ContainerBlockSize

https://codereview.chromium.org/2154593003 added
availableLogicalHeightForPercentageComputation, shared with the regular
percentage computation code, so this is definitely correct.

R=ikilpatrick@chromium.org,eae@chromium.org,glebl@chromium.org
BUG=635619

Review-Url: https://codereview.chromium.org/2323953002
Cr-Commit-Position: refs/heads/master@{#417427}
1 file changed