Lazily generate HistoryItem's serialized form state

Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 410 matching lines @@
     , m_compatibilityModeLocked(false)
     , m_hasAutofocused(false)
     , m_clearFocusedElementTimer(this, &Document::clearFocusedElementTimerFired)
     , m_domTreeVersion(++s_globalTreeVersion)
     , m_listenerTypes(0)
     , m_mutationObserverTypes(0)
     , m_visitedLinkState(VisitedLinkState::create(*this))
     , m_visuallyOrdered(false)
     , m_readyState(Complete)
     , m_isParsing(false)
-    , m_historyItemDocumentStateDirty(false)
     , m_gotoAnchorNeededAfterStylesheetsLoad(false)
     , m_containsValidityStyleRules(false)
     , m_updateFocusAppearanceRestoresSelection(false)
     , m_containsPlugins(false)
     , m_ignoreDestructiveWriteCount(0)
     , m_titleSetExplicitly(false)
     , m_markers(adoptPtr(new DocumentMarkerController))
     , m_updateFocusAppearanceTimer(this, &Document::updateFocusAppearanceTimerFired)
     , m_cssTarget(0)
     , m_loadEventProgress(LoadEventNotRun)
@@ skipping 1015 matching lines @@
     return "#document";
 }
 
 Node::NodeType Document::nodeType() const
 {
     return DOCUMENT_NODE;
 }
 
 FormController& Document::formController()
 {
-    if (!m_formController)
+    if (!m_formController) {
         m_formController = FormController::create();
+        if (m_frame && m_frame->loader().currentItem() && m_frame->loader().currentItem()->isCurrentDocument(this))
+            m_frame->loader().currentItem()->setDocumentState(m_formController->formElementsState());
+    }
     return *m_formController;
 }
 
-Vector<String> Document::formElementsState() const
+DocumentState* Document::formElementsState() const
 {
     if (!m_formController)
-        return Vector<String>();
+        return 0;
     return m_formController->formElementsState();
 }
 
 void Document::setStateForNewFormElements(const Vector<String>& stateVector)
 {
     if (!stateVector.size() && !m_formController)
         return;
     formController().setStateForNewFormElements(stateVector);
 }
 
@@ skipping 4090 matching lines @@
         (*it)->invalidateCache(attrName);
 }
 
 void Document::trace(Visitor* visitor)
 {
     Supplementable<Document>::trace(visitor);
     ContainerNode::trace(visitor);
 }
 
 } // namespace WebCore