[CSS Grid Layout] Remove old FIXME in RenderGrid::placeItemsOnGrid()

[CSS Grid Layout] Remove old FIXME in RenderGrid::placeItemsOnGrid()

There was a FIXME about not re-resolving positions if the grid is grown during
auto-placement. But as the spec has changed [1] and you can only refer to the
explicit grid (even if you use for example grid-column: 1 / -1). It seems that
we can get rid of this FIXME as it's not a causing a problem anymore.

[1] http://dev.w3.org/csswg/css-grid/#grid-placement-int

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=190608

[Manuel Rego, 2015-02-19 15:18:03]

rego@igalia.com changed reviewers:
+ cbiesinger@chromium.org, jchaffraix@chromium.org, leviw@chromium.org

[Julien - ping for review, 2015-02-21 00:34:10]

The CQ bit was checked by jchaffraix@chromium.org

[Julien - ping for review, 2015-02-21 00:34:10]

lgtm

[commit-bot: I haz the power, 2015-02-21 00:34:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/925593004/1

[commit-bot: I haz the power, 2015-02-21 01:57:09]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=190608