[Media Router WebUI] Remove unnecessary default property values.

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

Index: chrome/test/data/webui/media_router/issue_banner_tests.js
diff --git a/chrome/test/data/webui/media_router/issue_banner_tests.js b/chrome/test/data/webui/media_router/issue_banner_tests.js
index 7d9e0cc5b7bed63ceb9be044a7f0b50da5bc29ff..a5046b7b1c8cee47a396879569612dcdb66d3e15 100644
--- a/chrome/test/data/webui/media_router/issue_banner_tests.js
+++ b/chrome/test/data/webui/media_router/issue_banner_tests.js
@@ -166,9 +166,8 @@ cr.define('issue_banner', function() {
       // 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;