The above issue is reproducible on All-OS (Windows (10 & 7), Mac 10.11.4 & Ubuntu 14.04) with chrome versions : 50.2661.87(Stable), 51.0.2704.22(Beta) & 52.0.2714.0(Canary).
This is a non regression issue as can be seen from M30 build - 30.0.1549.0. Hence marking the same as Untriaged.

Thank you!

I believe this is a dup of bug 370604 -- Chris, can you confirm?

I don't think it is a duplicate of bug 370604 in the sense of compositing.
However, my guess is that it does involve PaintLayer. In this case there needs
to be some logic for re-ordering PaintLayers with the 'order' style.

Sorry, I misinterpreted the bug. This is actually wontfix:
https://lists.w3.org/Archives/Public/www-style/2016Apr/0351.htmlhttps://drafts.csswg.org/css-flexbox/issues-cr-20160301#issue-12

Please reopen the bug, because you have misunderstood the problem.

I'm very well aware of the recent CSSWG decision that the 'order' property
doesn't apply to abs.pos. elements.  This is NOT what this bug is about.

If you look at the testcase carefully, you will see that the abs.pos. elements
there does NOT even have 'order' specified on them.  The (in-flow) flex items
do though and it applies on those.  Again the spec is very very clear about
the effect it should have on flex items:
https://drafts.csswg.org/css-flexbox-1/#propdef-order
"This also affects the painting order [CSS21], exactly as if the flex items were reordered in the source document."

If you reorder the flex items manually, as I did in the testcase in
the flexbox at the bottom, that's how it should render.
IOW, 'order' on flex items should in fact affect the painting order of
descendant abs.pos. boxes just as it normally does on any other of its
child boxes.  (The CSSWG decision has nothing to do with this, it's
only about ignoring 'order' on the abs.pos. boxes themselves.)

The testcase works correctly in Firefox.

Moving this nonessential bug to the next milestone.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

This issue has been moved once and is lower than Pri-1. Removing the milestone.

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Bulk-adding Hotlist-Interop to bugs filed by other browser vendors based on the summary.  Feel free to remove if this issue doesn't actually reflect a difference in behavior between engines.

This issue has been Available for over a year. If it's no longer important or seems unlikely to be fixed, please consider closing it out. If it is important, please re-triage the issue.

Sorry for the inconvenience if the bug really should have been left as Available. If you change it back, also remove the "Hotlist-Recharge-Cold" label.

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This issue has been Available for over a year. If it's no longer important or seems unlikely to be fixed, please consider closing it out. If it is important, please re-triage the issue.

Sorry for the inconvenience if the bug really should have been left as Available.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot