Strip anonymous wrappers when a block flow no longer requires them

Source/core/layout/LayoutBlock.h

Index: Source/core/layout/LayoutBlock.h
diff --git a/Source/core/layout/LayoutBlock.h b/Source/core/layout/LayoutBlock.h
index a4393bf33b1dcf6b48f679e81dfc4e5baa120016..275b376bdf180751da7372dd4664d55bb99c5bdf 100644
--- a/Source/core/layout/LayoutBlock.h
+++ b/Source/core/layout/LayoutBlock.h
@@ -228,6 +228,11 @@ protected:
     void layout() override;
     bool updateImageLoadingPriorities() final;
 
+    enum AdjacentSiblings {
+        PreviousSiblings,
+        NextSiblings
+    };
+
     enum PositionedLayoutBehavior {
         DefaultLayout,
         LayoutOnlyFixedPositionedObjects,
@@ -318,6 +323,7 @@ private:
     void dirtyLinesFromChangedChild(LayoutObject* child) final { m_lineBoxes.dirtyLinesFromChangedChild(LineLayoutItem(this), LineLayoutItem(child)); }
 
     void addChildIgnoringContinuation(LayoutObject* newChild, LayoutObject* beforeChild) override;
+    void addAdjacentSiblingsToAnonymousBox(AdjacentSiblings, LayoutBlock* anonymousBox);
 
     bool isSelfCollapsingBlock() const override;