Move signin status and current user information into AppListModel.

ui/app_list/app_list_model_observer.h

Index: ui/app_list/app_list_model_observer.h
diff --git a/ui/app_list/app_list_model_observer.h b/ui/app_list/app_list_model_observer.h
index c843894c12f8baf15c21dfca2e91735ad865a3ed..a9545abfc875fa24a5716ddfb30a6cd21d69b514 100644
--- a/ui/app_list/app_list_model_observer.h
+++ b/ui/app_list/app_list_model_observer.h
@@ -12,8 +12,11 @@ namespace app_list {
 class APP_LIST_EXPORT AppListModelObserver {
  public:
   // Invoked when AppListModel's status has changed.
-  virtual void OnAppListModelStatusChanged() = 0;
-
+  virtual void OnAppListModelStatusChanged() {}

[tapted, 2013/08/06 09:27:50]

Observers are usually all pure-virtual, otherwise it raises questions about
multiple-inheritance, which is typically avoided in Chrome. I think these should
stay pure virtual.

[calamity, 2013/08/08 01:34:58]

This was discussed in https://codereview.chromium.org/16035013/. It seems to
come down to convenience vs purity. My preference is to avoid unnecessary empty
methods in inheritors but I'm willing to have it either way.

+  // Invoked when AppListModel's current user details have changed.
+  virtual void OnAppListModelProfilesChanged() {}
+  // Invoked when AppListModel's current user's signin status has changed.
+  virtual void OnAppListModelSigninStatusChanged() {}
  protected:

[tapted, 2013/08/06 09:27:50]

nit: blank line before protected:

[calamity, 2013/08/08 01:34:58]

Done.

   virtual ~AppListModelObserver() {}
 };