[CSS Grid Layout] Combining Content and Self Alignment with span items

[CSS Grid Layout] Combining Content and Self Alignment with span items

Using the Content Alignment CSS properties we can add offsets to the
grid tracks so they are not adjacent anymore. This requires to handle
Self Alignment of items spanning more than one track in a special way,
because grid item's area breadth is bigger than the tracks base size it
occupies.

In order to properly adjust the Self Alignment values we need to consider
the offset between tracks.

BUG=249451, 376823
Committed: https://crrev.com/42162f3d51bc0472475314a04661dfcc57096778
Cr-Commit-Position: refs/heads/master@{#352096}

[jfernandez, 2015-09-11 21:50:28]

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

[cbiesinger, 2015-09-30 15:09:02]

lgtm, but I'd add a comment to the endOfColumn adjustment saying something
similar to this change description, so that it's clearer what it's for.

[cbiesinger, 2015-09-30 15:09:10]

https://codereview.chromium.org/1342453004/diff/1/Source/core/layout/LayoutGr...
File Source/core/layout/LayoutGrid.cpp (right):

https://codereview.chromium.org/1342453004/diff/1/Source/core/layout/LayoutGr...
Source/core/layout/LayoutGrid.cpp:1760: return (distribution ==
ContentDistributionStretch || ContentDistributionStretch ==
ContentDistributionDefault) ? LayoutUnit(0) : trackPositions[1] -
trackPositions[0] - childBreadth;
Use LayoutUnit() instead of specifying the explicit zero, it's a bit faster

[jfernandez, 2015-10-02 16:16:37]

The CQ bit was checked by jfernandez@igalia.com

[jfernandez, 2015-10-02 16:16:37]

The patchset sent to the CQ was uploaded after l-g-t-m from
cbiesinger@chromium.org
Link to the patchset: https://codereview.chromium.org/1342453004/#ps60001
(title: "Added comment.")

[commit-bot: I haz the power, 2015-10-02 16:17:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1342453004/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1342453004/60001

[commit-bot: I haz the power, 2015-10-02 19:03:52]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2015-10-02 19:04:33]

Patchset 4 (id:??) landed as
https://crrev.com/42162f3d51bc0472475314a04661dfcc57096778
Cr-Commit-Position: refs/heads/master@{#352096}