arc: Implement proper Arc window activation for task moving to front.

chrome/browser/ui/app_list/arc/arc_app_list_prefs.h

Index: chrome/browser/ui/app_list/arc/arc_app_list_prefs.h
diff --git a/chrome/browser/ui/app_list/arc/arc_app_list_prefs.h b/chrome/browser/ui/app_list/arc/arc_app_list_prefs.h
index 907fa513ab1dfcd9e82387097825d50cf85919a9..25bfe628e6f8dd25918a083b34b9d0b1ecd0eaef 100644
--- a/chrome/browser/ui/app_list/arc/arc_app_list_prefs.h
+++ b/chrome/browser/ui/app_list/arc/arc_app_list_prefs.h
@@ -119,8 +119,10 @@ class ArcAppListPrefs
                                const std::string& activity) {}
     // Notifies that task has been destroyed.
     virtual void OnTaskDestroyed(int32_t task_id) {}
-    // Notifies that task has been activated and moved to the front.
+    // Notifies that task has been activated.
     virtual void OnTaskSetActive(int32_t task_id) {}
+    // Notifies that task has been moved to the front.
+    virtual void OnTaskMovedToFront(int32_t task_id) {}
 
     virtual void OnNotificationsEnabledChanged(
         const std::string& package_name, bool enabled) {}
@@ -232,6 +234,7 @@ class ArcAppListPrefs
                      const mojo::String& activity) override;
   void OnTaskDestroyed(int32_t task_id) override;
   void OnTaskSetActive(int32_t task_id) override;
+  void OnTaskMovedToFront(int32_t) override;
   void OnNotificationsEnabledChanged(const mojo::String& package_name,
                                      bool enabled) override;
   void OnPackageAdded(arc::mojom::ArcPackageInfoPtr package_info) override;