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

chrome/browser/ui/views/payments/order_summary_view_controller.cc

+// 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.
+
+#include "chrome/browser/ui/views/payments/order_summary_view_controller.h"
+
+#include "base/strings/utf_string_conversions.h"
+#include "chrome/browser/ui/views/payments/payment_request_dialog.h"
+#include "chrome/browser/ui/views/payments/payment_request_views_util.h"
+#include "chrome/grit/generated_resources.h"
+#include "ui/base/l10n/l10n_util.h"
+#include "ui/views/controls/button/md_text_button.h"
+#include "ui/views/layout/grid_layout.h"
+
+namespace {
+
+// The tag for the button that navigates back to the payment sheet.
+constexpr int kBackButtonTag = 0;
+
+}  // namespace
+
+namespace payments {
+
+// static
+std::unique_ptr<views::View> OrderSummaryViewController::CreateView(
+    OrderSummaryViewController* controller) {
+  views::View* content_view = new views::View;
+
+  views::GridLayout* layout = new views::GridLayout(content_view);
+  content_view->SetLayoutManager(layout);
+  views::ColumnSet* columns = layout->AddColumnSet(0);
+  columns->AddColumn(views::GridLayout::TRAILING, views::GridLayout::CENTER,
+                     0, views::GridLayout::USE_PREF, 0, 0);
+
+  layout->StartRow(0, 0);
+  views::LabelButton* back_button =
+      views::MdTextButton::CreateSecondaryUiBlueButton(
+          controller, base::ASCIIToUTF16("Back"));
+  back_button->set_tag(kBackButtonTag);
+  layout->AddView(back_button);
+
+  return payments::CreatePaymentView(
+      l10n_util::GetStringUTF16(IDS_PAYMENT_REQUEST_ORDER_SUMMARY_TITLE),
+      content_view);
+}
+
+OrderSummaryViewController::OrderSummaryViewController(
+    PaymentRequestImpl* impl, PaymentRequestDialog* dialog)
+  : PaymentRequestSheetController(impl, dialog) {}
+
+void OrderSummaryViewController::ButtonPressed(
+    views::Button* sender, const ui::Event& event) {
+  DCHECK_EQ(kBackButtonTag, sender->tag());
+
+  dialog()->GoBack();
+}
+
+}  // namespace payments