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

chrome/browser/chromeos/settings/device_settings_test_helper.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_CHROMEOS_SETTINGS_DEVICE_SETTINGS_TEST_HELPER_H_
 #define CHROME_BROWSER_CHROMEOS_SETTINGS_DEVICE_SETTINGS_TEST_HELPER_H_
 
 #include <map>
 #include <memory>
 #include <string>
@@ skipping 105 matching lines @@
       const std::string& policy_blob,
       const StorePolicyCallback& callback) override;
   void SetFlagsForUser(const cryptohome::Identification& cryptohome_id,
                        const std::vector<std::string>& flags) override;
   void GetServerBackedStateKeys(const StateKeysCallback& callback) override;
 
   void CheckArcAvailability(const ArcCallback& callback) override;
   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;
 
  private:
   struct PolicyState {
     bool store_result_;
     std::string policy_blob_;
     std::vector<StorePolicyCallback> store_callbacks_;
     std::vector<RetrievePolicyCallback> retrieve_callbacks_;
@@ skipping 62 matching lines @@
 
   std::unique_ptr<DBusThreadManagerSetter> dbus_setter_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DeviceSettingsTestBase);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_SETTINGS_DEVICE_SETTINGS_TEST_HELPER_H_