[Payments] Introduce basic interactive browsertests for Payment Request

components/payments/payment_request_web_contents_manager.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 "components/payments/payment_request_web_contents_manager.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/logging.h"
 #include "components/payments/payment_request_delegate.h"
 
 DEFINE_WEB_CONTENTS_USER_DATA_KEY(payments::PaymentRequestWebContentsManager);
 
 namespace payments {
 
 PaymentRequestWebContentsManager::~PaymentRequestWebContentsManager() {}
 
 PaymentRequestWebContentsManager*
 PaymentRequestWebContentsManager::GetOrCreateForWebContents(
     content::WebContents* web_contents) {
   DCHECK(web_contents);
-  // CreateForWebContents does nothing if the delegate instance already exists.
+  // CreateForWebContents does nothing if the manager instance already exists.
   PaymentRequestWebContentsManager::CreateForWebContents(web_contents);
   return PaymentRequestWebContentsManager::FromWebContents(web_contents);
 }
 
 void PaymentRequestWebContentsManager::CreatePaymentRequest(
     content::WebContents* web_contents,
     std::unique_ptr<PaymentRequestDelegate> delegate,
     mojo::InterfaceRequest<payments::mojom::PaymentRequest> request) {
   std::unique_ptr<PaymentRequest> new_request(new PaymentRequest(
       web_contents, std::move(delegate), this, std::move(request)));
   PaymentRequest* request_ptr = new_request.get();
   payment_requests_.insert(std::make_pair(request_ptr, std::move(new_request)));
 }
 
 void PaymentRequestWebContentsManager::DestroyRequest(PaymentRequest* request) {
   payment_requests_.erase(request);
 }
 
 PaymentRequestWebContentsManager::PaymentRequestWebContentsManager(
     content::WebContents* web_contents) {}
 
 }  // namespace payments