[LayoutNG] Very simple layout() implementation

Just resolved width and height, and returns a fragment with that.

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

Review-Url: https://codereview.chromium.org/2230563002
Cr-Commit-Position: refs/heads/master@{#410814}
2 files changed