[webnfc] Allow access to WebNFC API only from main frame

third_party/WebKit/LayoutTests/nfc/resources/nfc-helpers.js

 'use strict';
 
 var test_text_data = 'Test text data.';
 var test_text_byte_array = new TextEncoder('utf-8').encode(test_text_data);
 var test_number_data = 42;
 var test_json_data = {level: 1, score: 100, label: 'Game'};
 var test_url_data = 'https://w3c.github.io/web-nfc/';
 var test_message_origin = 'https://127.0.0.1:8443';
 var test_buffer_data = new ArrayBuffer(test_text_byte_array.length);
 var test_buffer_view = new Uint8Array(test_buffer_data).set(test_text_byte_array);
@@ skipping 388 matching lines @@
     }
 
     let mockNFC = new MockNFC;
     mojo.frameInterfaces.addInterfaceOverrideForTesting(
         nfc.NFC.name,
         handle => {
           mockNFC.bindingSet.addBinding(mockNFC, handle);
         });
 
     return Promise.resolve({
+      // Interface instance bound to main frame.
       mockNFC: mockNFC,
+      // Constructor for mock NFC class.
+      MockNFC: MockNFC,
+      // Loaded mojom interface.
+      NFC: nfc.NFC,
+      // Helper functions for comparing WebNFC structures.
       assertNFCMessagesEqual: assertNFCMessagesEqual,
       assertNFCPushOptionsEqual: assertNFCPushOptionsEqual,
       assertWebNFCMessagesEqual: assertWebNFCMessagesEqual,
       assertNFCWatchOptionsEqual: assertNFCWatchOptionsEqual,
     });
   });
 }
 
 function nfc_test(func, name, properties) {
   mojo_test(mojo => nfc_mocks(mojo).then(nfc => {
     let result = Promise.resolve(func(nfc));
     let cleanUp = () => nfc.mockNFC.reset();
     result.then(cleanUp, cleanUp);
     return result;
   }), name, properties);
 }