DRAFT CL: Add FrameNavigationEntry and track subframe session histories.

content/renderer/history_entry.h

Index: content/renderer/history_entry.h
diff --git a/content/renderer/history_entry.h b/content/renderer/history_entry.h
index 62da86a4692b8c244aba3696cf4dfbf3b4e5f01d..b9c9a19c0694561e22d066647b2300f5d8094ed1 100644
--- a/content/renderer/history_entry.h
+++ b/content/renderer/history_entry.h
@@ -79,6 +79,11 @@ class CONTENT_EXPORT HistoryEntry {
     blink::WebHistoryItem item_;
   };
 
+  // TODO(creis): Temporary hack to update RenderFrame routing ID -> FSN map
+  // when RenderFrames swap to RenderFrameProxies and back.  Remove when we
+  // don't need HistoryEntry anymore.
+  static void UpdateFrameMap(uint64_t old_routing_id, uint64_t new_routing_id);
+
   HistoryEntry(const blink::WebHistoryItem& root, int64_t frame_id);
   HistoryEntry();
   ~HistoryEntry();