Speed up ARC boot if the user launches ARC app while ARC is not ready

chrome/browser/chromeos/settings/device_settings_test_helper.h

Index: chrome/browser/chromeos/settings/device_settings_test_helper.h
diff --git a/chrome/browser/chromeos/settings/device_settings_test_helper.h b/chrome/browser/chromeos/settings/device_settings_test_helper.h
index 995791c66d5468cdd78a130da574e4c355298727..e034f1cd75a70a950eb71203309623c697a8048e 100644
--- a/chrome/browser/chromeos/settings/device_settings_test_helper.h
+++ b/chrome/browser/chromeos/settings/device_settings_test_helper.h
@@ -123,6 +123,7 @@ class DeviceSettingsTestHelper : public SessionManagerClient {
   void StartArcInstance(const cryptohome::Identification& cryptohome_id,
                         const ArcCallback& callback) override;
   void StopArcInstance(const ArcCallback& callback) override;
+  void PrioritizeArcInstance(const ArcCallback& callback) override;
   void GetArcStartTime(const GetArcStartTimeCallback& callback) override;
   void RemoveArcData(const cryptohome::Identification& cryptohome_id,
                      const ArcCallback& callback) override;