Separate PaymentRequest initialization and display.

third_party/WebKit/LayoutTests/payments/resources/payment-request-mock.js

 /*
  * payment-request-mock contains a mock implementation of PaymentRequest.
  */
 
 "use strict";
 
 let paymentRequestMock = loadMojoModules(
     'paymentRequestMock',
     ['third_party/WebKit/public/platform/modules/payments/payment_request.mojom',
      'mojo/public/js/router',
     ]).then(mojo => {
   let [paymentRequest, router] =  mojo.modules;
 
   class PaymentRequestMock {
     constructor(interfaceProvider) {
       interfaceProvider.addInterfaceOverrideForTesting(
         paymentRequest.PaymentRequest.name,
         handle => this.connectPaymentRequest_(handle));
 
       this.interfaceProvider_ = interfaceProvider;
       this.pendingResponse_ = null;
     }
 
     connectPaymentRequest_(handle) {
       this.paymentRequestStub_ = new paymentRequest.PaymentRequest.stubClass(this);
       this.paymentRequestRouter_ = new router.Router(handle);
       this.paymentRequestRouter_.setIncomingReceiver(this.paymentRequestStub_);
     }
 
-    setClient(client) {
+    init(client, supportedMethods, details, options) {
       this.client_ = client;
       if (this.pendingResponse_) {
         let response = this.pendingResponse_;
         this.pendingResponse_ = null;
         this.onPaymentResponse(response);
       }
     }
 
-    show(supportedMethods, details, options, stringifiedData) {
+    show() {
     }
 
     updateWith(details) {
     }
 
     complete(success) {
     }
 
     onPaymentResponse(data) {
       if (!this.client_) {
         this.pendingResponse_ = data;
         return;
       }
       this.client_.onPaymentResponse(new paymentRequest.PaymentResponse(data));
     }
 
     onComplete() {
       this.client_.onComplete();
     }
   }
   return new PaymentRequestMock(mojo.frameInterfaces);
 });