Adding overview / layer framework to Activities so that unloaded / sleeping activities can be shown…

athena/content/app_activity_registry.h

Index: athena/content/app_activity_registry.h
diff --git a/athena/content/app_activity_registry.h b/athena/content/app_activity_registry.h
index c2dbd65a48298dc46bdf1106eae9a573e2f63782..a0f5dbb4a2e1fac3635c962c4c1be3e8d071258c 100644
--- a/athena/content/app_activity_registry.h
+++ b/athena/content/app_activity_registry.h
@@ -74,6 +74,10 @@ class ATHENA_EXPORT AppActivityRegistry {
   void RestartApplication(AppActivityProxy* proxy);
 
  private:
+  // Called if an unload of an application should take place asynchronously to
+  // avoid object destruction within an observer handler.
+  void DelayedUnload();
+
   // Gets most recently used AppAcitivty that belongs to the same application.
   AppActivity* GetMruActivity();