Lazily generate HistoryItem's serialized form state

Source/core/testing/Internals.cpp

Index: Source/core/testing/Internals.cpp
diff --git a/Source/core/testing/Internals.cpp b/Source/core/testing/Internals.cpp
index d750094d7fd7e76deb9acdaa2599a501e7ff8e31..573aa8a71a640a4f3f26fa594a5772bdbd28e7da 100644
--- a/Source/core/testing/Internals.cpp
+++ b/Source/core/testing/Internals.cpp
@@ -742,6 +742,7 @@ void Internals::setFormControlStateOfHistoryItem(const Vector<String>& state, Ex
         exceptionState.throwDOMException(InvalidAccessError, "No history item is available.");
         return;
     }
+    mainItem->clearDocumentState();
     mainItem->setDocumentState(state);
 }
 
@@ -2099,8 +2100,7 @@ PassRefPtrWillBeRawPtr<TypeConversions> Internals::typeConversions() const
 
 Vector<String> Internals::getReferencedFilePaths() const
 {
-    frame()->loader().saveDocumentState();
-    return FormController::getReferencedFilePaths(frame()->loader().currentItem()->documentState());
+    return frame()->loader().currentItem()->getReferencedFilePaths();
 }
 
 void Internals::startTrackingRepaints(Document* document, ExceptionState& exceptionState)