Dynamic updating recent menu for tabs from other devices.

components/browser_sync/profile_sync_service.h

Index: components/browser_sync/profile_sync_service.h
diff --git a/components/browser_sync/profile_sync_service.h b/components/browser_sync/profile_sync_service.h
index 7048a483f899c0dd998749f02a638d8fbc3049eb..3680d23c250854a6761faec3418337f7429d899f 100644
--- a/components/browser_sync/profile_sync_service.h
+++ b/components/browser_sync/profile_sync_service.h
@@ -58,6 +58,7 @@
 
 class Profile;
 class ProfileOAuth2TokenService;
+class RecentTabsSubMenuModelTest;
 class SigninManagerWrapper;
 
 namespace sync_sessions {
@@ -612,6 +613,7 @@ class ProfileSyncService : public syncer::SyncServiceBase,
   };
 
   friend class TestProfileSyncService;
+  friend class ::RecentTabsSubMenuModelTest;

[Peter Kasting, 2017/03/23 04:48:35]

Is there a way to test this functionality without using private APIs?  If not,
I'm inclined to suggest refactoring so there is.  I'm uncomfortable with a
random toolbar test needing to reach into the internals of a sync class.

For example, make the recent tabs submenu model have a mockable or injectable
data source, so it doesn't need to talk to sync at all in test code.

 
   // Helper to install and configure a data type manager.
   void ConfigureDataTypeManager();