[Media Router WebUI] Remove unnecessary default property values.

chrome/test/data/webui/media_router/issue_banner_tests.js

 // Copyright 2015 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.
 
 /** @fileoverview Suite of tests for issue-banner. */
 cr.define('issue_banner', function() {
   function registerTests() {
     suite('IssueBanner', function() {
       /**
        * Issue Banner created before each test.
@@ skipping 148 matching lines @@
           checkDataFromEventFiring(fakeNonBlockingIssueOne,
               data, false);
           done();
         });
         MockInteractions.tap(banner.$['opt-button']);
       });
 
       // Tests the issue text. While the UI will show only the blocking or
       // non-blocking interface, the issue's info will be set if specified.
       test('issue text', function() {
-        // |issue| is null. Title text should be empty.
-        assertEquals(null, banner.issue);
-        checkIssueText(banner.issue);
+        // |issue| is initially undefined.
+        assertEquals(undefined, banner.issue);
 
         // Set |issue| to be a blocking issue. Title text should be updated.
         banner.issue = fakeBlockingIssueOne;
         checkIssueText(banner.issue);
 
         // Set |issue| to be a non-blocking issue. Title text should be
         // updated.
         banner.issue = fakeNonBlockingIssueOne;
         checkIssueText(banner.issue);
       });
@@ skipping 17 matching lines @@
         banner.issue = fakeNonBlockingIssueTwo;
         checkButtonVisibility(fakeNonBlockingIssueTwo.secondaryActionType);
       });
     });
   }
 
   return {
     registerTests: registerTests,
   };
 });