[Signin Error Dialog] (2/3) Added handlers and UI constructors

chrome/browser/ui/webui/signin/signin_error_ui.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_UI_WEBUI_SIGNIN_SIGNIN_ERROR_UI_H_
+#define CHROME_BROWSER_UI_WEBUI_SIGNIN_SIGNIN_ERROR_UI_H_
+
+#include "base/macros.h"
+#include "ui/web_dialogs/web_dialog_ui.h"
+
+class SigninErrorHandler;
+
+namespace ui {
+class WebUI;
+}
+
+class SigninErrorUI : public ui::WebDialogUI {
+ public:
+  explicit SigninErrorUI(content::WebUI* web_ui);
+  // Used to inject a SigninErrorHandler in tests.
+  SigninErrorUI(content::WebUI* web_ui, SigninErrorHandler* handler);
+  ~SigninErrorUI() override {}
+
+  DISALLOW_COPY_AND_ASSIGN(SigninErrorUI);
+};
+
+#endif  // CHROME_BROWSER_UI_WEBUI_SIGNIN_SIGNIN_ERROR_UI_H_