[CSS Grid Layout] Fix crash in positioned items placed on implicit grid

[CSS Grid Layout] Fix crash in positioned items placed on implicit grid

If we don't check that the initial and final positions are inside the
current grid we could be trying to access undefined positions in the
columns/rows positions arrays.

BUG=273898
TEST=fast/css-grid-layout/grid-positioned-items-implicit-grid.html

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=186840

[Manuel Rego, 2014-12-07 21:22:27]

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

[Manuel Rego, 2014-12-07 21:22:28]

This issue was introduced in r186610.

[Julien - ping for review, 2014-12-09 18:49:53]

lgtm

https://codereview.chromium.org/769683004/diff/1/Source/core/rendering/Render...
File Source/core/rendering/RenderGrid.cpp (right):

https://codereview.chromium.org/769683004/diff/1/Source/core/rendering/Render...
Source/core/rendering/RenderGrid.cpp:1233: finalPosition =
std::min<GridResolvedPosition>(finalPosition, lastPosition);
I think we need to put a comment as to why we do that. The only reason is that
positioned items don't grow the grid so we could end up outside of it.

Note that this is going to be super weird: we can end up putting them outside
the grid element as the grid is not grown.

[Manuel Rego, 2014-12-10 08:41:57]

https://codereview.chromium.org/769683004/diff/1/Source/core/rendering/Render...
File Source/core/rendering/RenderGrid.cpp (right):

https://codereview.chromium.org/769683004/diff/1/Source/core/rendering/Render...
Source/core/rendering/RenderGrid.cpp:1233: finalPosition =
std::min<GridResolvedPosition>(finalPosition, lastPosition);
On 2014/12/09 18:49:53, Julien Chaffraix - PST wrote:
> I think we need to put a comment as to why we do that. The only reason is that
> positioned items don't grow the grid so we could end up outside of it.

Done.

[Manuel Rego, 2014-12-10 08:42:02]

The CQ bit was checked by rego@igalia.com

[commit-bot: I haz the power, 2014-12-10 08:42:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/769683004/20001

[commit-bot: I haz the power, 2014-12-10 09:55:30]

Committed patchset #2 (id:20001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=186840