Bug 1523595 Part 2 - Add missing NS_FRAME_HAS_MULTI_COLUMN_ANCESTOR for nested ColumnSetWrapper. r=dbaron

Bug 1507244 changes how NS_FRAME_HAS_MULTI_COLUMN_ANCESTOR is propagated
to the child, but I forget to add the bit for nested ColumnSetWrapper.

Currently, no other code depends on this bit being set on nested
ColumnSetWrapper, but Part 3 will. Without this patch,
testing/web-platform/tests/css/css-multicol/multicol-nested-margin-002.xht
will fail with Part 3.

Differential Revision: https://phabricator.services.mozilla.com/D31675

--HG--
extra : moz-landing-system : lando

layout/base/nsCSSFrameConstructor.cpp

@@ -10698,6 +10698,10 @@ nsContainerFrame* nsCSSFrameConstructor::BeginBuildingColumns(
   nsBlockFrame* columnSetWrapper = NS_NewColumnSetWrapperFrame(
       mPresShell, aComputedStyle, nsFrameState(NS_FRAME_OWNS_ANON_BOXES));
   InitAndRestoreFrame(aState, aContent, aParentFrame, columnSetWrapper);
+  if (aParentFrame->HasAnyStateBits(NS_FRAME_HAS_MULTI_COLUMN_ANCESTOR) &&
+      !ShouldSuppressColumnSpanDescendants(aParentFrame)) {
+    columnSetWrapper->AddStateBits(NS_FRAME_HAS_MULTI_COLUMN_ANCESTOR);
+  }
 
   RefPtr<ComputedStyle> columnSetStyle =
       mPresShell->StyleSet()->ResolveInheritingAnonymousBoxStyle(