[Payments] Introduce basic interactive browsertests for Payment Request

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

+// Copyright 2017 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/test_chrome_payment_request_delegate.h"
+
+#include "content/public/browser/web_contents.h"
+
+namespace payments {
+
+TestChromePaymentRequestDelegate::TestChromePaymentRequestDelegate(
+    content::WebContents* web_contents,
+    PaymentRequestDialog::ObserverForTest* observer)
+    : ChromePaymentRequestDelegate(web_contents), observer_(observer) {}
+
+void TestChromePaymentRequestDelegate::ShowPaymentRequestDialog(
+    PaymentRequest* request) {
+  PaymentRequestDialog::ShowWebModalPaymentDialog(
+      new PaymentRequestDialog(request, observer_), request);
+}
+
+}  // namespace payments