DRAFT CL: Add FrameNavigationEntry and track subframe session histories.

content/renderer/history_entry.cc

Index: content/renderer/history_entry.cc
diff --git a/content/renderer/history_entry.cc b/content/renderer/history_entry.cc
index 7686165f4eea2c131e1cb51a800383429b6277f9..cf98e028b00fb78994275d793577b3344605983d 100644
--- a/content/renderer/history_entry.cc
+++ b/content/renderer/history_entry.cc
@@ -54,6 +54,15 @@ static FrameMap& GetFrameMap() {
   return routing_ids_to_internal_frame_ids;
 }
 
+// static
+void HistoryEntry::UpdateFrameMap(uint64_t old_routing_id,
+                                  uint64_t new_routing_id) {
+  if (GetFrameMap()[old_routing_id]) {
+    GetFrameMap()[new_routing_id] = GetFrameMap()[old_routing_id];
+    GetFrameMap().erase(old_routing_id);
+  }
+}
+
 HistoryEntry::HistoryNode* HistoryEntry::HistoryNode::AddChild(
     const WebHistoryItem& item,
     int64_t frame_id) {