Split the frame tree logic out of HistoryItem

Source/web/WebHistoryItem.cpp

Index: Source/web/WebHistoryItem.cpp
diff --git a/Source/web/WebHistoryItem.cpp b/Source/web/WebHistoryItem.cpp
index 612fcfa89305ae47c92936e57f9f4c448b601411..d3ad6439c2ce56b649b6ba89a09606939db91203 100644
--- a/Source/web/WebHistoryItem.cpp
+++ b/Source/web/WebHistoryItem.cpp
@@ -174,7 +174,6 @@ long long WebHistoryItem::itemSequenceNumber() const
 void WebHistoryItem::setItemSequenceNumber(long long itemSequenceNumber)
 {
     ensureMutable();
-    m_private->setItemSequenceNumber(itemSequenceNumber);
 }
 
 long long WebHistoryItem::documentSequenceNumber() const
@@ -185,7 +184,6 @@ long long WebHistoryItem::documentSequenceNumber() const
 void WebHistoryItem::setDocumentSequenceNumber(long long documentSequenceNumber)
 {
     ensureMutable();
-    m_private->setDocumentSequenceNumber(documentSequenceNumber);
 }
 
 WebSerializedScriptValue WebHistoryItem::stateObject() const
@@ -226,6 +224,14 @@ WebVector<WebHistoryItem> WebHistoryItem::children() const
     return m_private->children();
 }
 
+void WebHistoryItem::setChildren(const WebVector<WebHistoryItem>& items)
+{
+    ensureMutable();
+    m_private->clearChildren();
+    for (size_t i = 0; i < items.size(); ++i)
+        m_private->addChildItem(items[i]);
+}
+
 void WebHistoryItem::appendToChildren(const WebHistoryItem& item)
 {
     ensureMutable();