arc: Fix default app availability reporting.

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 3dce5be03a67eb73e01eaedfef1c8ab34eef0f70..d36f80ec00c53f6dc5ee830ed001ae6b8eab942a 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
@@ -360,6 +360,8 @@ class ArcAppListPrefs
   base::FilePath base_path_;
   // Contains set of ARC apps that are currently ready.
   std::unordered_set<std::string> ready_apps_;
+  // Contains set of ARC apps that are currently tracked.
+  std::unordered_set<std::string> tracked_apps_;
   // Keeps deferred icon load requests. Each app may contain several requests
   // for different scale factor. Scale factor is defined by specific bit
   // position.