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

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 <string>
 
@@ skipping 16 matching lines @@
 constexpr int kPaymentRequestRowVerticalInsets = 8;
 
 // Extra inset relative to the header when a right edge should line up with the
 // close button's X rather than its invisible right edge.
 constexpr int kPaymentRequestRowExtraRightInset = 8;
 constexpr int kPaymentRequestButtonSpacing = 10;
 
 enum class PaymentRequestCommonTags {
   BACK_BUTTON_TAG = 0,
   CLOSE_BUTTON_TAG,
+  PAY_BUTTON_TAG,
   // This is the max value of tags for controls common to multiple
   // PaymentRequest contexts. Individual screens that handle both common and
   // specific events with tags can start their specific tags at this value.
   PAYMENT_REQUEST_COMMON_TAG_MAX
 };
 
 // Creates and returns a header for all the sheets in the PaymentRequest dialog.
 // The header contains an optional back arrow button (if |show_back_arrow| is
 // true), a |title| label. |delegate| becomes the delegate for the back and
 // close buttons.
@@ skipping 32 matching lines @@
     bool show_payer_email,
     bool show_payer_phone);
 
 // Creates a views::Border object that can paint the gray horizontal ruler used
 // as a separator between items in the Payment Request dialog.
 std::unique_ptr<views::Border> CreatePaymentRequestRowBorder();
 
 }  // namespace payments
 
 #endif  // CHROME_BROWSER_UI_VIEWS_PAYMENTS_PAYMENT_REQUEST_VIEWS_UTIL_H_