[Payments] Add Payment Request metrics for selected payment method.

chrome/test/data/android/payments/metrics.js

 /*
  * 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.
  */
 
 /* global PaymentRequest:false */
 /* global toDictionary:false */
 
 var request;
 
 /**
  * Launches the PaymentRequest UI that accepts credit cards.
  */
-function buy() {  // eslint-disable-line no-unused-vars
+function ccBuy() {  // eslint-disable-line no-unused-vars
   try {
     request = new PaymentRequest(
         [{supportedMethods: ['visa']}], {
           total: {label: 'Total', amount: {currency: 'USD', value: '5.00'}},
           shippingOptions: [{
             id: 'freeShippingOption',
             label: 'Free global shipping',
             amount: {currency: 'USD', value: '0'},
             selected: true
           }]
@@ skipping 14 matching lines @@
         });
   } catch (error) {
     print(error.message);
   }
 }
 
 /**
  * Launches the PaymentRequest UI which accepts a supported payment method but
  * does not accept credit cards.
  */
-function noMatching() {  // eslint-disable-line no-unused-vars
+function bobPayBuy() {  // eslint-disable-line no-unused-vars
   try {
     request = new PaymentRequest(
         [{supportedMethods: ['https://bobpay.com']}], {
           total: {label: 'Total', amount: {currency: 'USD', value: '5.00'}},
           shippingOptions: [{
             id: 'freeShippingOption',
             label: 'Free global shipping',
             amount: {currency: 'USD', value: '0'},
             selected: true
           }]
@@ skipping 59 matching lines @@
   try {
     request.abort().then(function() {
       print('Aborted');
     }).catch(function() {
       print('Cannot abort');
     });
   } catch (error) {
     print(error.message);
   }
 }