[Payments] Add the pay button, and control its enabled state

chrome/browser/ui/views/payments/payment_request_dialog_view.h

Index: chrome/browser/ui/views/payments/payment_request_dialog_view.h
diff --git a/chrome/browser/ui/views/payments/payment_request_dialog_view.h b/chrome/browser/ui/views/payments/payment_request_dialog_view.h
index 53b784e84a856e8886c984e8f32311a932a3775d..a50fb8abb46141200f0831ef54cf1223cc562029 100644
--- a/chrome/browser/ui/views/payments/payment_request_dialog_view.h
+++ b/chrome/browser/ui/views/payments/payment_request_dialog_view.h
@@ -61,6 +61,7 @@ class PaymentRequestDialogView : public views::DialogDelegateView,
   // payments::PaymentRequestDialog
   void ShowDialog() override;
   void CloseDialog() override;
+  void UpdatePayButtonState(bool enabled) override;
 
   void GoBack();
   void ShowOrderSummary();
@@ -86,6 +87,10 @@ class PaymentRequestDialogView : public views::DialogDelegateView,
   ControllerMap controller_map_;
   ViewStack view_stack_;
 
+  // Used to lookup the payment sheet view controller. Weak reference that is
+  // nullified when the view is removed from the hierarchy.
+  views::View* payment_sheet_view_;
+
   // May be null.
   ObserverForTest* observer_for_testing_;