arc: Enable silent PlayStore Sign-In.

chrome/browser/chromeos/arc/arc_auth_code_fetcher_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_AUTH_CODE_FETCHER_DELEGATE_H_
+#define CHROME_BROWSER_CHROMEOS_ARC_ARC_AUTH_CODE_FETCHER_DELEGATE_H_
+
+namespace arc {
+
+class ArcAuthCodeFetcherDelegate {
+ public:
+  virtual void OnAuthCodeSuccess(const std::string& auth_code) = 0;
+  virtual void OnAuthCodeFailed() = 0;
+
+ protected:
+  virtual ~ArcAuthCodeFetcherDelegate() {}
+};
+
+}  // namespace arc
+
+#endif  // CHROME_BROWSER_CHROMEOS_ARC_ARC_AUTH_CODE_FETCHER_DELEGATE_H_