Move header chaser tree_ to protected, for test.

include/bitcoin/node/chasers/chaser_header.hpp

@@ -31,7 +31,7 @@ namespace node {
 class full_node;
 
 /// Chase down stronger header branches for the candidate chain.
-/// Weak branches are retained in a hash table unless already store populated.
+/// Weak branches are retained in a hash table if not store populated.
 /// Strong branches reorganize the candidate chain and fire the 'header' event.
 class BCN_API chaser_header
   : public chaser
@@ -48,8 +48,16 @@ class BCN_API chaser_header
         system::chain::context&& context) NOEXCEPT;
 
 protected:
+    struct proposed_header
+    {
+        database::context context;
+        system::chain::header::cptr header;
+    };
     typedef std::vector<database::header_link> header_links;
 
+    // This is protected by strand.
+    std::unordered_map<system::hash_digest, proposed_header> tree_{};
+
     /// Handlers.
     virtual void handle_event(const code& ec, chase event_,
         link value) NOEXCEPT;
@@ -81,18 +89,11 @@ class BCN_API chaser_header
     virtual bool push(const system::hash_digest& key) NOEXCEPT;
 
 private:
-    struct proposed_header
-    {
-        database::context context;
-        system::chain::header::cptr header;
-    };
-
     void do_handle_event(const code& ec, chase event_, link value) NOEXCEPT;
     void do_organize(const system::chain::header::cptr& header,
         const system::chain::context& context) NOEXCEPT;
 
-    // These are protected by strand.
-    std::unordered_map<system::hash_digest, proposed_header> tree_{};
+    // These are thread safe.
     const network::wall_clock::duration currency_window_;
     const bool use_currency_window_;
 };