[css-grid] Add support for orthogonal positioned grid items
This patch adds support for positioned grid items with orthogonal flows.
Basically it just needs to check if the item is orthogonal to use
the column or row offset as logical left or top depending on the case.
Added new tests for WPT repository under: css/css-grid-1/abspos/
Two of these new tests are failing due to an issue with margins
and orthogonal items, which is unrelated to this patch (see bug #725903).
BUG=639873
Change-Id: Ic6aef9eef46a8a254678aac8958f0976cb53e89c
Reviewed-on: https://chromium-review.googlesource.com/513965
Reviewed-by: Javier Fernandez <jfernandez@igalia.com>
Commit-Queue: Manuel Rego Casasnovas <rego@igalia.com>
Cr-Commit-Position: refs/heads/master@{#474335}32 files changed
