[traffic] Update clear/purge logic to use update mechanism

Signed-off-by: mvglasow <michael -at- vonglasow.com>

map/traffic_manager.cpp

@@ -157,7 +157,6 @@ void TrafficManager::Clear()
 #endif
     m_messageCache.clear();
     m_feedQueue.clear();
-    m_allMwmColoring.clear();
     m_mwmCache.clear();
 
     // TODO figure out which of the ones below we still need
@@ -411,6 +410,12 @@ void TrafficManager::Push(traffxml::TraffFeed feed)
 }
 
 void TrafficManager::PurgeExpiredMessages()
+{
+  PurgeExpiredMessagesImpl();
+  OnTrafficDataUpdate();
+}
+
+void TrafficManager::PurgeExpiredMessagesImpl()
 {
   std::lock_guard<std::mutex> lock(m_mutex);
   LOG(LINFO, ("before:", m_messageCache.size(), "message(s)"));
@@ -549,7 +554,7 @@ void TrafficManager::ThreadRoutine()
       if (steady_clock::now() - lastPurged >= kPurgeInterval)
       {
         lastPurged == steady_clock::now();
-        PurgeExpiredMessages();
+        PurgeExpiredMessagesImpl();
       }
 
       LOG(LINFO, ("active MWMs changed:", m_activeMwmsChanged, ", poll needed:", m_isPollNeeded));

map/traffic_manager.hpp

@@ -219,7 +219,7 @@ public:
   /**
    * @brief Purges expired messages from the cache.
    *
-   * This method is safe to call from any thread.
+   * This method is safe to call from any thread, except for the traffic worker thread.
    */
   void PurgeExpiredMessages();
 
@@ -352,6 +352,15 @@ private:
    */
   bool Poll();
 
+  /**
+   * @brief Purges expired messages from the cache.
+   *
+   * This is the internal conterpart of `PurgeExpiredMessages()`. It is safe to call from any
+   * thread. Unlike `PurgeExpiredMessages()`, it does not wake the worker thread, making it suitable
+   * for use on the worker thread.
+   */
+  void PurgeExpiredMessagesImpl();
+
   /**
    * @brief Consolidates the feed queue.
    *