Introduce SigninManagerDelegate and use to eliminate CookieSettings dependency.

chrome/browser/signin/signin_manager_delegate.h

+// Copyright 2013 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_SIGNIN_SIGNIN_MANAGER_DELEGATE_H_
+#define CHROME_BROWSER_SIGNIN_SIGNIN_MANAGER_DELEGATE_H_
+
+// A delegate interface that needs to be supplied to SigninManager by
+// the embedder.
+class SigninManagerDelegate {
+ public:
+  virtual ~SigninManagerDelegate() {}
+
+  // Returns true if the cookie policy for the execution context of
+  // the SigninManager allows cookies for the Google signin domain.
+  virtual bool AreSigninCookiesAllowed() = 0;
+};
+
+#endif  // CHROME_BROWSER_SIGNIN_SIGNIN_MANAGER_DELEGATE_H_