arc: Implement silent OptIn mode for managed Arc.

chrome/browser/chromeos/arc/arc_android_management_checker_delegate.h

 // Copyright 2016 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_ARC_ARC_ANDROID_MANAGEMENT_CHECKER_DELEGATE_H_
 #define CHROME_BROWSER_CHROMEOS_ARC_ARC_ANDROID_MANAGEMENT_CHECKER_DELEGATE_H_
 
 #include "chrome/browser/chromeos/policy/android_management_client.h"
 
+namespace arc {
+
 class ArcAndroidManagementCheckerDelegate {
  public:
   virtual void OnAndroidManagementChecked(
       policy::AndroidManagementClient::Result result) = 0;
 
  protected:
   virtual ~ArcAndroidManagementCheckerDelegate() {}
 };
 
+}  // namespace arc
+
 #endif  // CHROME_BROWSER_CHROMEOS_ARC_ARC_ANDROID_MANAGEMENT_CHECKER_DELEGATE_H_