Split the frame tree logic out of HistoryItem

Source/core/loader/FrameLoaderTypes.h

Index: Source/core/loader/FrameLoaderTypes.h
diff --git a/Source/core/loader/FrameLoaderTypes.h b/Source/core/loader/FrameLoaderTypes.h
index cb0e73bf7e9ce8ddf7a7b72b2960c37b2866361b..05a784eb1de91e39ffeac8dbee0d8d0799baac29 100644
--- a/Source/core/loader/FrameLoaderTypes.h
+++ b/Source/core/loader/FrameLoaderTypes.h
@@ -93,6 +93,11 @@ namespace WebCore {
         SameDocumentNavigationPushState,
         SameDocumentNavigationReplaceState
     };
+
+    enum HistoryLoadType {
+        HistorySameDocumentLoad,
+        HistoryDifferentDocumentLoad
+    };
 }
 
 #endif