gdata: Support mouting archive file in GData cache

chrome/browser/chromeos/extensions/file_browser_event_router.cc

Index: chrome/browser/chromeos/extensions/file_browser_event_router.cc
diff --git a/chrome/browser/chromeos/extensions/file_browser_event_router.cc b/chrome/browser/chromeos/extensions/file_browser_event_router.cc
index 87c9dfae8948d849bafcb61420cb0f547c7c6f7d..9e97f57226f22949863cc5642b8538ab9c6f3f3f 100644
--- a/chrome/browser/chromeos/extensions/file_browser_event_router.cc
+++ b/chrome/browser/chromeos/extensions/file_browser_event_router.cc
@@ -414,9 +414,10 @@ void FileBrowserEventRouter::OnDiskAdded(
 
   // If disk is not mounted yet and it has media, give it a try.
   if (disk->mount_path().empty() && disk->has_media()) {
-    // Initiate disk mount operation.
+    // Initiate disk mount operation. Here MountPath auto-detects the
+    // filesystem format if the second argument is empty.
     DiskMountManager::GetInstance()->MountPath(
-        disk->device_path(), chromeos::MOUNT_TYPE_DEVICE);
+        disk->device_path(), std::string(), chromeos::MOUNT_TYPE_DEVICE);
   } else {
     // Either the disk was mounted or it has no media. In both cases we don't
     // want the Scanning notification to persist.
@@ -482,8 +483,8 @@ void FileBrowserEventRouter::OnFormattingFinished(
     // Hide it after a couple of seconds.
     notifications_->HideNotificationDelayed(
         FileBrowserNotifications::FORMAT_SUCCESS, device_path, 4000);
-
-    DiskMountManager::GetInstance()->MountPath(device_path,
+    // MountPath auto-detects filesystem format if second argument is empty.
+    DiskMountManager::GetInstance()->MountPath(device_path, std::string(),
                                                chromeos::MOUNT_TYPE_DEVICE);
   } else {
     notifications_->HideNotification(FileBrowserNotifications::FORMAT_START,