[LayoutNG] Rename logical_available_size to container_size.

From: crrev.com/2727263003

The percentage resolution size should be based off the container, and the
available size should remain as-is.

BUG=635619

Review-Url: https://codereview.chromium.org/2729213002
Cr-Commit-Position: refs/heads/master@{#454637}
1 file changed