[WebPayments] Factor out sheet-specific logic in Controllers.

chrome/browser/ui/views/payments/payment_request_views_util.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_VIEWS_PAYMENTS_PAYMENT_REQUEST_VIEWS_UTIL_H_
+#define CHROME_BROWSER_UI_VIEWS_PAYMENTS_PAYMENT_REQUEST_VIEWS_UTIL_H_
+
+#include <memory>
+
+#include "base/strings/string16.h"
+
+namespace views {
+class View;
+}
+
+namespace payments {
+
+// Creates a view to be displayed in the PaymentRequestDialog. |title| is the
+// text displayed on top of the dialog and |content_view| is displayed between
+// the title and the pay/cancel buttons.
+std::unique_ptr<views::View> CreatePaymentView(
+    const base::string16& title, views::View* content_view);
+
+}  // namespace payments
+
+#endif  // CHROME_BROWSER_UI_VIEWS_PAYMENTS_PAYMENT_REQUEST_VIEWS_UTIL_H_