Add a dialog for getting user consent in the echo redeem flow.

chrome/browser/ui/echo_dialog_listener_chromeos.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_UI_ECHO_DIALOG_LISTENER_CHROMEOS_H_
+#define CHROME_BROWSER_UI_ECHO_DIALOG_LISTENER_CHROMEOS_H_
+
+// A listener interface for the EchoDialog, so an interested party can be
+// notified about changes to the dialog. It is provided during EchoDialog
+// construction.
+class EchoDialogListener {
+ public:
+  // Called when the EchoDialog is accepted. After call to this method, the
+  // listener will not be invoked again.
+  virtual void OnAccept() = 0;
+
+  // Called when the EchoDialog is canceled. After call to this method, the
+  // listener will not be invoked again.
+  virtual void OnCancel() = 0;
+
+  // Called when a link in the EchoDialog is clicked.
+  virtual void OnMoreInfoLinkClicked() = 0;
+
+ protected:
+  virtual ~EchoDialogListener() {}
+};
+
+#endif  // CHROME_BROWSER_UI_ECHO_DIALOG_LISTENER_CHROMEOS_H_