Only re-use an anonymous block for continuations if it's contained by a block flow.

third_party/WebKit/Source/core/layout/LayoutInline.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 419 matching lines @@
 void LayoutInline::splitFlow(LayoutObject* beforeChild, LayoutBlock* newBlockBox,
     LayoutObject* newChild, LayoutBoxModelObject* oldCont)
 {
     LayoutBlockFlow* containingBlockFlow = toLayoutBlockFlow(containingBlock());
     LayoutBlock* pre = nullptr;
     LayoutBlock* block = containingBlockFlow;
 
     // Delete our line boxes before we do the inline split into continuations.
     containingBlockFlow->deleteLineBoxTree();
 
-    bool madeNewBeforeBlock = false;
-    if (block->isAnonymousBlock() && (!block->parent() || !block->parent()->createsAnonymousWrapper())) {
-        // We can reuse this block and make it the preBlock of the next continuation.
-        containingBlockFlow->removePositionedObjects(nullptr);
-        containingBlockFlow->removeFloatingObjects();
-        pre = containingBlockFlow;
-        block = block->containingBlock();
-    } else {
-        // No anonymous block available for use.  Make one.
-        pre = block->createAnonymousBlock();
-        madeNewBeforeBlock = true;
+    bool reusedAnonymousBlock = false;
+    if (block->isAnonymousBlock()) {
+        LayoutBlock* outerContainingBlock = block->containingBlock();
+        if (outerContainingBlock
+            && outerContainingBlock->isLayoutBlockFlow()
+            && !outerContainingBlock->createsAnonymousWrapper()) {
+            // We can reuse this block and make it the preBlock of the next continuation.
+            containingBlockFlow->removePositionedObjects(nullptr);
+            containingBlockFlow->removeFloatingObjects();
+            pre = containingBlockFlow;
+            block = outerContainingBlock;
+            reusedAnonymousBlock = true;
+        }
     }
+    if (!reusedAnonymousBlock)
+        pre = block->createAnonymousBlock(); // No anonymous block available for use. Make one.
 
     LayoutBlock* post = toLayoutBlock(pre->createAnonymousBoxWithSameTypeAs(block));
 
-    LayoutObject* boxFirst = madeNewBeforeBlock ? block->firstChild() : pre->nextSibling();
-    if (madeNewBeforeBlock)
+    LayoutObject* boxFirst = !reusedAnonymousBlock ? block->firstChild() : pre->nextSibling();
+    if (!reusedAnonymousBlock)
         block->children()->insertChildNode(block, pre, boxFirst);
     block->children()->insertChildNode(block, newBlockBox, boxFirst);
     block->children()->insertChildNode(block, post, boxFirst);
     block->setChildrenInline(false);
 
-    if (madeNewBeforeBlock) {
+    if (!reusedAnonymousBlock) {
         LayoutObject* o = boxFirst;
         while (o) {
             LayoutObject* no = o;
             o = no->nextSibling();
             pre->children()->appendChildNode(pre, block->children()->removeChildNode(block, no));
             no->setNeedsLayoutAndPrefWidthsRecalcAndFullPaintInvalidation(LayoutInvalidationReason::AnonymousBlockChange);
         }
     }
 
     splitInlines(pre, post, newBlockBox, beforeChild, oldCont);
@@ skipping 880 matching lines @@
 
 void LayoutInline::invalidateDisplayItemClients(const LayoutBoxModelObject& paintInvalidationContainer, PaintInvalidationReason invalidationReason) const
 {
     LayoutBoxModelObject::invalidateDisplayItemClients(paintInvalidationContainer, invalidationReason);
 
     for (InlineFlowBox* box = firstLineBox(); box; box = box->nextLineBox())
         paintInvalidationContainer.invalidateDisplayItemClientOnBacking(*box, invalidationReason);
 }
 
 } // namespace blink