[New Multicolumn] Simplified layout also needs to mark spanner placeholders for layout.

Source/core/layout/LayoutBlockFlow.cpp

Index: Source/core/layout/LayoutBlockFlow.cpp
diff --git a/Source/core/layout/LayoutBlockFlow.cpp b/Source/core/layout/LayoutBlockFlow.cpp
index dfcebdc15f07bae306b16ed8f99c1a3684d8cde0..543d12b4c9e8ffa25c90f69ed899e8b58fa7206f 100644
--- a/Source/core/layout/LayoutBlockFlow.cpp
+++ b/Source/core/layout/LayoutBlockFlow.cpp
@@ -2007,11 +2007,8 @@ void LayoutBlockFlow::styleDidChange(StyleDifference diff, const ComputedStyle*
 
 void LayoutBlockFlow::updateBlockChildDirtyBitsBeforeLayout(bool relayoutChildren, LayoutBox& child)
 {
-    if (child.isLayoutMultiColumnSpannerPlaceholder() && toLayoutMultiColumnSpannerPlaceholder(child).layoutObjectInFlowThread()->needsLayout()) {
-        // The containing block of a spanner is the multicol container (|this| block), but the spanner
-        // is laid out via its spanner set (|child|), so we need to make sure that we enter it.
-        child.setChildNeedsLayout(MarkOnlyThis);
-    }
+    if (child.isLayoutMultiColumnSpannerPlaceholder())
+        toLayoutMultiColumnSpannerPlaceholder(child).markForLayoutIfObjectInFlowThreadNeedsLayout();
     LayoutBlock::updateBlockChildDirtyBitsBeforeLayout(relayoutChildren, child);
 }