Subtree caching implementation in blink-core

Source/core/layout/LayoutText.cpp

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Andrew Wellington (proton@wiretapped.net)
  * Copyright (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *
  * 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
@@ skipping 1860 matching lines @@
         gSecureTextTimers->add(this, secureTextTimer);
     }
     secureTextTimer->restartWithNewText(lastTypedCharacterOffset);
 }
 
 PassRefPtr<AbstractInlineTextBox> LayoutText::firstAbstractInlineTextBox()
 {
     return AbstractInlineTextBox::getOrCreate(this, m_firstTextBox);
 }
 
-void LayoutText::invalidateDisplayItemClients(const LayoutBoxModelObject& paintInvalidationContainer) const
+void LayoutText::invalidateDisplayItemClients(const LayoutBoxModelObject& paintInvalidationContainer)
 {
     LayoutObject::invalidateDisplayItemClients(paintInvalidationContainer);
     for (InlineTextBox* box = firstTextBox(); box; box = box->nextTextBox()) {
         paintInvalidationContainer.invalidateDisplayItemClientOnBacking(*box);
         if (box->truncation() != cNoTruncation) {
             if (EllipsisBox* ellipsisBox = box->root().ellipsisBox())
                 paintInvalidationContainer.invalidateDisplayItemClientOnBacking(*ellipsisBox);
         }
     }
 }
 
 } // namespace blink