Storage manager: Hide "Offline files" when Google Drive volume is not mounted.

chrome/browser/ui/webui/options/chromeos/storage_manager_handler.cc

Index: chrome/browser/ui/webui/options/chromeos/storage_manager_handler.cc
diff --git a/chrome/browser/ui/webui/options/chromeos/storage_manager_handler.cc b/chrome/browser/ui/webui/options/chromeos/storage_manager_handler.cc
index c49798d764f261c46692fb2e4b9c0184739108bf..a64edc1108631478c5677568fb40fdee1ef77499 100644
--- a/chrome/browser/ui/webui/options/chromeos/storage_manager_handler.cc
+++ b/chrome/browser/ui/webui/options/chromeos/storage_manager_handler.cc
@@ -269,10 +269,16 @@ void StorageManagerHandler::OnGetDownloadsSize(int64_t size) {
 void StorageManagerHandler::UpdateDriveCacheSize() {
   if (updating_drive_cache_size_)
     return;
-  updating_drive_cache_size_ = true;
 
   drive::FileSystemInterface* const file_system =
       drive::util::GetFileSystemByProfile(Profile::FromWebUI(web_ui()));
+  if (!file_system)
+    return;
+
+  // Shows the item "Offline cache" and start calculating size.
+  web_ui()->CallJavascriptFunctionUnsafe(
+      "options.StorageManager.showDriveCacheItem");
+  updating_drive_cache_size_ = true;
   file_system->CalculateCacheSize(
       base::Bind(&StorageManagerHandler::OnGetDriveCacheSize,
                  weak_ptr_factory_.GetWeakPtr()));