[LayoutNG] Fix broken layout while using CSS with writing modes.

1) This will set a writing mode to the fragment builder so it can be used at the time when we calculate a physical fragment.
2) Change computeMargin to accept 2 more parameters: Direction and writing mode.

TEST=NGBlockLayoutAlgorithmTest.LayoutBlockChildrenWithWritingMode
BUG=635619

Review-Url: https://codereview.chromium.org/2347773002
Cr-Commit-Position: refs/heads/master@{#419309}
11 files changed