Started in https://ci.chromium.org/buildbot/chromium.webkit/WebKit%20Mac10.10/47757

Dunno why SoM isn't complaining.

Suspecting

[LayoutNG] Make LayoutNGFlexibleBox inherit from LayoutBlock

It previously inherited from LayoutNGBlockFlow, which, aside from
violating is-a, prevented inline flex children from being blockified --
LayoutNGBlockFlow::AddChild does not call LayoutBlock::AddChild, which
is where the blockification happens.

Considered inheriting from LayoutFlexibleBox to get better baseline and
intrinsic size support, but those will have to be reimplemented in
LayoutNG anyway.

With this change, IsLayoutNGMixin() is e
...skip...
/flexbox/button-expected.png is because the underline
in the link is 1 pixel shorter.

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Change-Id: I42811edeb53e8e2a80a64d5b30bf6627e0957b7d
Bug: 845235
Reviewed-on: https://chromium-review.googlesource.com/1062499
Commit-Queue: David Grogan <dgrogan@chromium.org>
Reviewed-by: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#561661}


I'll just skip it on Mac for now. I suspect it's some rebaselineing issue.