[WebPayments] Implement state transitions in desktop WebPayments dialog.

chrome/browser/payments/ui/payment_request_dialog.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_PAYMENTS_UI_PAYMENT_REQUEST_DIALOG_H_
 #define CHROME_BROWSER_PAYMENTS_UI_PAYMENT_REQUEST_DIALOG_H_
 
+#include "chrome/browser/payments/ui/order_summary_state.h"
+#include "chrome/browser/payments/ui/payment_dialog_state.h"
+#include "chrome/browser/payments/ui/payment_sheet_state.h"
 #include "components/payments/payment_request.mojom.h"
+#include "ui/views/animation/bounds_animator.h"
 #include "ui/views/controls/label.h"
 #include "ui/views/window/dialog_delegate.h"
 
 namespace payments {
 
-class PaymentRequestDialog : public views::DialogDelegateView {
+class PaymentRequestDialog : public views::DialogDelegateView,
+                             public PaymentSheetState::Observer,
+                             public OrderSummaryState::Observer {
  public:
   explicit PaymentRequestDialog(
       payments::mojom::PaymentRequestClientPtr client);
   ~PaymentRequestDialog() override;
 
+  void PushState(std::unique_ptr<PaymentDialogState> state);
+  void PopState();
+
   // views::WidgetDelegate
   ui::ModalType GetModalType() const override;
 
   // views::View
   gfx::Size GetPreferredSize() const override;
 
   // views::DialogDelegate
   bool Cancel() override;
 
+  // PaymentSheetState::Observer:
+  void OnOrderSummaryClicked() override;
+
+  // OrderSummaryState::Observer:
+  void OnBackClicked() override;
+
  private:
   payments::mojom::PaymentRequestClientPtr client_;
-  std::unique_ptr<views::Label> label_;
+  std::unique_ptr<views::BoundsAnimator> slide_in_animator_;
+  std::unique_ptr<views::BoundsAnimator> slide_out_animator_;
+
+  std::stack<std::unique_ptr<PaymentDialogState> > state_stack_;
 
   DISALLOW_COPY_AND_ASSIGN(PaymentRequestDialog);
 };
 
 }  // namespace payments
 
 #endif  // CHROME_BROWSER_PAYMENTS_UI_PAYMENT_REQUEST_DIALOG_H_