Lazily generate HistoryItem's serialized form state

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index 94af56c0c40277a1b7c5976aefe59891e6418b9f..3163af1a419d824a7448c4a8e47fb4a06d38f0ec 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -427,7 +427,6 @@ Document::Document(const DocumentInit& initializer, DocumentClassFlags documentC
     , m_visuallyOrdered(false)
     , m_readyState(Complete)
     , m_isParsing(false)
-    , m_historyItemDocumentStateDirty(false)
     , m_gotoAnchorNeededAfterStylesheetsLoad(false)
     , m_containsValidityStyleRules(false)
     , m_updateFocusAppearanceRestoresSelection(false)
@@ -1465,15 +1464,18 @@ Node::NodeType Document::nodeType() const
 
 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());

[abarth-chromium, 2014/04/17 23:41:24]

It seems slightly odd that getting the formController would store data on the
current history item as a side-effect...  I guess the idea is that if you don't
have a formController then the DocumentState is zero...

[Nate Chapin, 2014/04/17 23:48:19]

Right. I didn't see a cleaner way to hook this up. I guess maybe FormController
is cheap enough to construct that we could just initialize it greedily?

+    }
     return *m_formController;
 }
 
-Vector<String> Document::formElementsState() const
+DocumentState* Document::formElementsState() const
 {
     if (!m_formController)
-        return Vector<String>();
+        return 0;
     return m_formController->formElementsState();
 }