[css-grid] Fix static position for positioned grid items

[css-grid] Fix static position for positioned grid items

The spec was updated to define properly the static position
for positioned grid items, but we didn't update the implementation yet:
https://drafts.csswg.org/css-grid-1/issues-wd-20150108#issue-1

We were only setting the static position when the start line
was not auto. Otherwise we were using the default one
which includes the padding.
With the spec change we need to set it always,
even if the start line is auto.

Updated several tests to follow the new expected behavior.

BUG=607137
Committed: https://crrev.com/92d518467d7a6ff962ae2c3c8c44c903e9472ef0
Cr-Commit-Position: refs/heads/master@{#390215}

[Manuel Rego, 2016-04-27 12:00:57]

rego@igalia.com changed reviewers:
+ cbiesinger@chromium.org, jfernandez@igalia.com, svillar@igalia.com

[cbiesinger, 2016-04-27 16:28:25]

lgtm

[Manuel Rego, 2016-04-27 19:22:44]

The CQ bit was checked by rego@igalia.com

[commit-bot: I haz the power, 2016-04-27 19:23:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1929483002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1929483002/1

[commit-bot: I haz the power, 2016-04-27 22:24:29]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-04-30 17:13:57]

Patchset 1 (id:??) landed as
https://crrev.com/92d518467d7a6ff962ae2c3c8c44c903e9472ef0
Cr-Commit-Position: refs/heads/master@{#390215}

[commit-bot: I haz the power, 2016-04-30 17:52:28]

Description was changed from

==========
[css-grid] Fix static position for positioned grid items

The spec was updated to define properly the static position
for positioned grid items, but we didn't update the implementation yet:
https://drafts.csswg.org/css-grid-1/issues-wd-20150108#issue-1

We were only setting the static position when the start line
was not auto. Otherwise we were using the default one
which includes the padding.
With the spec change we need to set it always,
even if the start line is auto.

Updated several tests to follow the new expected behavior.

BUG=607137
==========

to

==========
[css-grid] Fix static position for positioned grid items

The spec was updated to define properly the static position
for positioned grid items, but we didn't update the implementation yet:
https://drafts.csswg.org/css-grid-1/issues-wd-20150108#issue-1

We were only setting the static position when the start line
was not auto. Otherwise we were using the default one
which includes the padding.
With the spec change we need to set it always,
even if the start line is auto.

Updated several tests to follow the new expected behavior.

BUG=607137

Committed: https://crrev.com/92d518467d7a6ff962ae2c3c8c44c903e9472ef0
Cr-Commit-Position: refs/heads/master@{#390215}
==========