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

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

Index: chrome/browser/ui/views/payments/payment_sheet_view_controller.h
diff --git a/chrome/browser/ui/views/payments/payment_sheet_view_controller.h b/chrome/browser/ui/views/payments/payment_sheet_view_controller.h
index a442991d9ec77dda6d2dc6ba388552f4b2f1561f..3bda260cb57f1a6b5cd1df664969adf3e2ea54c0 100644
--- a/chrome/browser/ui/views/payments/payment_sheet_view_controller.h
+++ b/chrome/browser/ui/views/payments/payment_sheet_view_controller.h
@@ -26,6 +26,9 @@ class PaymentSheetViewController : public PaymentRequestSheetController {
 
   // PaymentRequestSheetController:
   std::unique_ptr<views::View> CreateView() override;
+  std::unique_ptr<views::Button> CreatePrimaryButton() override;
+
+  void UpdatePayButtonState(bool enabled);
 
  private:
   // PaymentRequestSheetController:
@@ -39,6 +42,8 @@ class PaymentSheetViewController : public PaymentRequestSheetController {
   std::unique_ptr<views::View> CreateContactInfoSectionContent();
   std::unique_ptr<views::Button> CreateContactInfoRow();
 
+  views::Button* pay_button_;
+
   const int widest_name_column_view_width_;
 
   DISALLOW_COPY_AND_ASSIGN(PaymentSheetViewController);