win: Make MusicManagerPrivateTest.DeviceIdValueReturned work on swarming.

chrome/test/data/extensions/platform_apps/music_manager_private/device_id_value_returned/chrometest.js

Index: chrome/test/data/extensions/platform_apps/music_manager_private/device_id_value_returned/chrometest.js
diff --git a/chrome/test/data/extensions/platform_apps/music_manager_private/device_id_value_returned/chrometest.js b/chrome/test/data/extensions/platform_apps/music_manager_private/device_id_value_returned/chrometest.js
index 8d4539c1e4d5f7052e04982dbf9ea1c0138740da..93be223dc235178b2ffff449bf78b0369907e2bb 100644
--- a/chrome/test/data/extensions/platform_apps/music_manager_private/device_id_value_returned/chrometest.js
+++ b/chrome/test/data/extensions/platform_apps/music_manager_private/device_id_value_returned/chrometest.js
@@ -2,16 +2,14 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-var deviceIdMaybeUndefined;
-
 function runTests() {
   chrome.test.runTests([
     function test() {
       chrome.musicManagerPrivate.getDeviceId(function(id) {
           console.log('Device ID=' + id);
-          if (!id) {
-            chrome.test.assertEq(true, deviceIdMaybeUndefined)
-          } else {
+          if (id) {
+            // This block is not entered in VMs (e.g. the bots) which return
+            // dummy MACs.
             chrome.test.assertEq('string', typeof id);
             chrome.test.assertTrue(id.length >= 8);
           }
@@ -24,8 +22,6 @@ function runTests() {
 window.onload = function() {
   chrome.test.getConfig(function(config) {
     console.log('customArg=' + config.customArg);
-    deviceIdMaybeUndefined =
-        (config.customArg === 'device_id_may_be_undefined');
     runTests();
   });
 }