Add an unittest for background/volume_manager.js

chrome/browser/chromeos/file_manager/file_manager_jstest.cc

Index: chrome/browser/chromeos/file_manager/file_manager_jstest.cc
diff --git a/chrome/browser/chromeos/file_manager/file_manager_jstest.cc b/chrome/browser/chromeos/file_manager/file_manager_jstest.cc
index b0b970615ad9075cbd31982b3afdd0823b14b98c..9547a1b6b62418ec38668addaa34068dc84f8af8 100644
--- a/chrome/browser/chromeos/file_manager/file_manager_jstest.cc
+++ b/chrome/browser/chromeos/file_manager/file_manager_jstest.cc
@@ -65,3 +65,8 @@ IN_PROC_BROWSER_TEST_F(FileManagerJsTest, ImportHistoryTest) {
   RunTest(base::FilePath(
       FILE_PATH_LITERAL("import_history_unittest.html")));
 }
+
+IN_PROC_BROWSER_TEST_F(FileManagerJsTest, VolumeManagerTest) {
+  RunTest(base::FilePath(
+      FILE_PATH_LITERAL("volume_manager_unittest.html")));
+}