Make SelectionEditor::markCacheDirty() not to reset cached value if it has been cleared

third_party/WebKit/Source/core/editing/SelectionEditor.cpp

 /*
  * Copyright (C) 2004, 2008, 2009, 2010 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 105 matching lines @@
 
 bool SelectionEditor::isContentEditable() const {
   return computeVisibleSelectionInDOMTree().isContentEditable();
 }
 
 bool SelectionEditor::isContentRichlyEditable() const {
   return computeVisibleSelectionInDOMTree().isContentRichlyEditable();
 }
 
 void SelectionEditor::markCacheDirty() {
+  if (m_cacheIsDirty)
+    return;
   m_cachedVisibleSelectionInFlatTree = VisibleSelectionInFlatTree();
   m_cachedVisibleSelectionInDOMTree = VisibleSelection();
   m_cacheIsDirty = true;
 }
 
 void SelectionEditor::setSelection(const SelectionInDOMTree& newSelection) {
   newSelection.assertValidFor(document());
   if (m_selection == newSelection)
     return;
   resetLogicalRange();
@@ skipping 115 matching lines @@
   visitor->trace(m_frame);
   visitor->trace(m_selection);
   visitor->trace(m_cachedVisibleSelectionInDOMTree);
   visitor->trace(m_cachedVisibleSelectionInFlatTree);
   visitor->trace(m_logicalRange);
   visitor->trace(m_cachedRange);
   SynchronousMutationObserver::trace(visitor);
 }
 
 }  // namespace blink