Ensure the text autosizer creates a root cluster when needed

Source/core/layout/TextAutosizer.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 125 matching lines @@
         return false;
     const Element* element = toElement(node);
 
     return (element->isFormControlElement() && !isHTMLTextAreaElement(element));
 }
 
 static bool isPotentialClusterRoot(const LayoutObject* layoutObject)
 {
     // "Potential cluster roots" are the smallest unit for which we can
     // enable/disable text autosizing.
+    // - Must have children.
+    //   An exception is made for LayoutView which should create a root to
+    //   maintain consistency with documents that have no child nodes but may
+    //   still have LayoutObject children.
     // - Must not be inline, as different multipliers on one line looks terrible.
     //   Exceptions are inline-block and alike elements (inline-table, -webkit-inline-*),
     //   as they often contain entire multi-line columns of text.
     // - Must not be normal list items, as items in the same list should look
     //   consistent, unless they are floating or position:absolute/fixed.
     Node* node = layoutObject->generatingNode();
-    if (node && !node->hasChildren())
+    if (node && !node->hasChildren() && !layoutObject->isLayoutView())
         return false;
     if (!layoutObject->isLayoutBlock())
         return false;
     if (layoutObject->isInline() && !layoutObject->style()->isDisplayReplacedType())
         return false;
     if (layoutObject->isListItem())
         return (layoutObject->isFloating() || layoutObject->isOutOfFlowPositioned());
 
     return true;
 }
@@ skipping 145 matching lines @@
 {
     if (!m_pageInfo.m_settingEnabled && !m_fingerprintMapper.hasFingerprints())
         return;
 
     ASSERT(!m_blocksThatHaveBegunLayout.contains(block));
 
     if (m_fingerprintMapper.remove(block) && m_firstBlockToBeginLayout) {
         // LayoutBlock with a fingerprint was destroyed during layout.
         // Clear the cluster stack and the supercluster map to avoid stale pointers.
         // Speculative fix for http://crbug.com/369485.
-        m_firstBlockToBeginLayout = 0;
+        m_firstBlockToBeginLayout = nullptr;
         m_clusterStack.clear();
         m_superclusters.clear();
     }
 }
 
 TextAutosizer::BeginLayoutBehavior TextAutosizer::prepareForLayout(const LayoutBlock* block)
 {
 #if ENABLE(ASSERT)
     m_blocksThatHaveBegunLayout.add(block);
 #endif
@@ skipping 26 matching lines @@
     }
 }
 
 void TextAutosizer::beginLayout(LayoutBlock* block)
 {
     ASSERT(shouldHandleLayout());
 
     if (prepareForLayout(block) == StopLayout)
         return;
 
+    ASSERT(!m_clusterStack.isEmpty() || block->isLayoutView());
+
     if (Cluster* cluster = maybeCreateCluster(block))
         m_clusterStack.append(adoptPtr(cluster));
 
+    ASSERT(!m_clusterStack.isEmpty());
+
     // Cells in auto-layout tables are handled separately by inflateAutoTable.
     bool isAutoTableCell = block->isTableCell() && !toLayoutTableCell(block)->table()->style()->isFixedTableLayout();
     if (!isAutoTableCell && !m_clusterStack.isEmpty())
         inflate(block);
 }
 
 void TextAutosizer::inflateAutoTable(LayoutTable* table)
 {
     ASSERT(table);
     ASSERT(!table->style()->isFixedTableLayout());
@@ skipping 19 matching lines @@
             }
         }
     }
 }
 
 void TextAutosizer::endLayout(LayoutBlock* block)
 {
     ASSERT(shouldHandleLayout());
 
     if (block == m_firstBlockToBeginLayout) {
-        m_firstBlockToBeginLayout = 0;
+        m_firstBlockToBeginLayout = nullptr;
         m_clusterStack.clear();
         m_superclusters.clear();
         m_stylesRetainedDuringLayout.clear();
 #if ENABLE(ASSERT)
         m_blocksThatHaveBegunLayout.clear();
 #endif
     // Tables can create two layout scopes for the same block so the isEmpty
     // check below is needed to guard against endLayout being called twice.
     } else if (!m_clusterStack.isEmpty() && currentCluster()->m_root == block) {
         m_clusterStack.removeLast();
@@ skipping 755 matching lines @@
     }
     return computedSize;
 }
 
 DEFINE_TRACE(TextAutosizer)
 {
     visitor->trace(m_document);
 }
 
 } // namespace blink