Introduce Identity Service and its initial usage

chrome/browser/extensions/api/identity/identity_get_profile_user_info_function.h

 // Copyright 2017 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_EXTENSIONS_API_IDENTITY_IDENTITY_GET_PROFILE_USER_INFO_FUNCTION_H_
 #define CHROME_BROWSER_EXTENSIONS_API_IDENTITY_IDENTITY_GET_PROFILE_USER_INFO_FUNCTION_H_
 
 #include "chrome/browser/extensions/chrome_extension_function.h"
+#include "components/signin/core/account_id/account_id.h"
 #include "extensions/browser/extension_function_histogram_value.h"
+#include "services/identity/public/interfaces/identity_manager.mojom.h"
 
 namespace extensions {
 
 class IdentityGetProfileUserInfoFunction
     : public ChromeUIThreadExtensionFunction {
  public:
   DECLARE_EXTENSION_FUNCTION("identity.getProfileUserInfo",
                              IDENTITY_GETPROFILEUSERINFO);
 
   IdentityGetProfileUserInfoFunction();
 
  private:
   ~IdentityGetProfileUserInfoFunction() override;
+  void OnReceivedPrimaryAccountId(const base::Optional<AccountId>& account_id);
 
   // UIThreadExtensionFunction implementation.
   ExtensionFunction::ResponseAction Run() override;
+
+  identity::mojom::IdentityManagerPtr identity_manager_;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_IDENTITY_IDENTITY_GET_PROFILE_USER_INFO_FUNCTION_H_