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This is a reland of 4e246b2e
Original change's description:
> [LayoutNG] Don't let legacy layout re-enter layout of a scrollable block node.
>
> We'd end up re-entering NGBlockNode::CopyFragmentDataToLayoutBox() for
> the same node.
>
> After layout of a fragment, NGBlockNode::CopyFragmentDataToLayoutBox() would
> call LayoutBlock::UpdateAfterLayout(), which would call
> scrollbar was toggled, it'd go ahead and call UpdateLayout() on the object,
> which would take us back into the NG layout machinery, on the same node, via
> Finally we'd re-enter NGBlockNode::CopyFragmentDataToLayoutBox(), causing misc
> kinds of misery, such as not being able to paint the block at all. For
> multicol, there'd even be a DCHECK failure "Variable fragment inline size not
> supported", because the code got confused as to whether a fragment was a first
> fragment or not.
>
> LayoutBox: :UpdateAfterLayout(), which would call
> PaintLayer: :UpdateSizeAndScrollingAfterLayout(), which would call
> PaintLayerScrollableArea: :UpdateAfterLayout(). If this code detected that a
> LayoutNGBlockFlow: :UpdateBlockLayout(), further to NGBlockNode::Layout().
> Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_layout_ng;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
> Change-Id: I832372223e324682bb4e38b3177dce30093df2e1
> Reviewed-on: https://chromium-review.googlesource.com/824265
> Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
> Reviewed-by: Emil A Eklund <eae@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#524039}

TBR=eae@chromium.org

Change-Id: I5aceb5c45c8fa60b20fa481318f05c609ca2b46b
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_layout_ng;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Reviewed-on: https://chromium-review.googlesource.com/826985Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524074}