[sync] WebContentsObserver based sessions notifications

components/sync_sessions/sessions_sync_manager.h

Index: components/sync_sessions/sessions_sync_manager.h
diff --git a/components/sync_sessions/sessions_sync_manager.h b/components/sync_sessions/sessions_sync_manager.h
index d685c65cd42b58f7cb22d4b2b3b6810761165eec..2513fc7a064c1dec4bc3a6d4e2f44bb92b14b091 100644
--- a/components/sync_sessions/sessions_sync_manager.h
+++ b/components/sync_sessions/sessions_sync_manager.h
@@ -62,7 +62,7 @@ class SessionsSyncManager : public syncer::SyncableService,
   SessionsSyncManager(SyncSessionsClient* sessions_client,
                       syncer::SyncPrefs* sync_prefs,
                       syncer::LocalDeviceInfoProvider* local_device,
-                      std::unique_ptr<LocalSessionEventRouter> router,
+                      LocalSessionEventRouter* router,
                       const base::Closure& sessions_updated_callback,
                       const base::Closure& datatype_refresh_callback);
   ~SessionsSyncManager() override;
@@ -309,7 +309,7 @@ class SessionsSyncManager : public syncer::SyncableService,
   // stale and a candidate for garbage collection.
   int stale_session_threshold_days_;
 
-  std::unique_ptr<LocalSessionEventRouter> local_event_router_;
+  LocalSessionEventRouter* local_event_router_;
 
   // Owns revisiting instrumentation logic for page visit events.
   PageRevisitBroadcaster page_revisit_broadcaster_;