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 ce6b1407a347fc13b76fceb2ade7e7f671398489..0fd1f662cf1dbe3640ac13197ab197e741162378 100644
--- a/Source/web/WebHistoryItem.cpp
+++ b/Source/web/WebHistoryItem.cpp
@@ -188,6 +188,17 @@ void WebHistoryItem::setDocumentSequenceNumber(long long documentSequenceNumber)
     m_private->setDocumentSequenceNumber(documentSequenceNumber);
 }
 
+long long WebHistoryItem::targetFrameID() const
+{
+    return m_private->targetFrameID();
+}
+
+void WebHistoryItem::setTargetFrameID(long long targetFrameID)
+{
+    ensureMutable();
+    m_private->setTargetFrameID(targetFrameID);
+}
+
 WebSerializedScriptValue WebHistoryItem::stateObject() const
 {
     return WebSerializedScriptValue(m_private->stateObject());
@@ -226,6 +237,14 @@ 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();