Adding a format device button to UI.

chrome/test/data/extensions/api_test/filebrowser_mount/test.html

Index: chrome/test/data/extensions/api_test/filebrowser_mount/test.html
diff --git a/chrome/test/data/extensions/api_test/filebrowser_mount/test.html b/chrome/test/data/extensions/api_test/filebrowser_mount/test.html
index f3cdb90ad3fd740f836f8b1cbd65b3a0334257c0..387bc7e5042c55dadeb9acd664adb23185bde25f 100644
--- a/chrome/test/data/extensions/api_test/filebrowser_mount/test.html
+++ b/chrome/test/data/extensions/api_test/filebrowser_mount/test.html
@@ -2,7 +2,7 @@
 // These have to be sync'd with extension_file_browser_private_apitest.cc
 var expectedVolume1 = {
   devicePath: 'device_path1',
-  mountPath: 'mount_path1',
+  mountPath: 'removable/mount_path1',
   systemPath: 'system_path1',
   filePath: 'file_path1',
   deviceLabel: 'device_label1',
@@ -18,6 +18,7 @@ var expectedVolume1 = {
 var expectedVolume2 = {
   devicePath: 'device_path2',
   mountPath: 'mount_path2',
+  mountPath: 'removable/mount_path2',
   systemPath: 'system_path2',
   filePath: 'file_path2',
   deviceLabel: 'device_label2',
@@ -33,6 +34,7 @@ var expectedVolume2 = {
 var expectedVolume3 = {
   devicePath: 'device_path3',
   mountPath: 'mount_path3',
+  mountPath: 'removable/mount_path3',
   systemPath: 'system_path3',
   filePath: 'file_path3',
   deviceLabel: 'device_label3',