arc: ARC loading progress should not be shown when started from OOBE.

chrome/browser/chromeos/arc/arc_support_host.h

Index: chrome/browser/chromeos/arc/arc_support_host.h
diff --git a/chrome/browser/chromeos/arc/arc_support_host.h b/chrome/browser/chromeos/arc/arc_support_host.h
index 9a33c41a17166439747d8b4cd5e7df56e72940a2..2b73fd354b0c4e548d4b922a075a05f94ac4d279 100644
--- a/chrome/browser/chromeos/arc/arc_support_host.h
+++ b/chrome/browser/chromeos/arc/arc_support_host.h
@@ -92,6 +92,10 @@ class ArcSupportHost : public arc::ArcSupportMessageHost::Observer,
   // is started.
   void SetArcManaged(bool is_arc_managed);
 
+  // Sets silent mode that suppresses the showing UI page on low priority UI
+  // events such as Arc loading progress.
+  void SetSilentMode();
+
   // Requests to close the extension window.
   void Close();
 
@@ -182,6 +186,10 @@ class ArcSupportHost : public arc::ArcSupportMessageHost::Observer,
 
   bool is_arc_managed_ = false;
 
+  // Silent mode suppresses the showing UI page on low priority UI events such
+  // as Arc loading progress.
+  bool silent_mode_ = false;
+
   PreferenceCheckboxData metrics_checkbox_;
   PreferenceCheckboxData backup_and_restore_checkbox_;
   PreferenceCheckboxData location_services_checkbox_;