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

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/webui/options/chromeos/storage_manager_handler.h"
 
 #include <algorithm>
 #include <numeric>
 #include <string>
 
@@ skipping 251 matching lines @@
 void StorageManagerHandler::OnGetDownloadsSize(int64_t size) {
   updating_downloads_size_ = false;
   web_ui()->CallJavascriptFunctionUnsafe(
       "options.StorageManager.setDownloadsSize",
       base::StringValue(ui::FormatBytes(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()));
 }
 
 void StorageManagerHandler::OnGetDriveCacheSize(int64_t size) {
   updating_drive_cache_size_ = false;
   web_ui()->CallJavascriptFunctionUnsafe(
       "options.StorageManager.setDriveCacheSize",
       base::StringValue(ui::FormatBytes(size)));
@@ skipping 151 matching lines @@
   web_ui()->CallJavascriptFunctionUnsafe("options.StorageManager.setArcSize",
                                          base::StringValue(size_string));
 }
 
 void StorageManagerHandler::OnClearDriveCacheDone(bool success) {
   UpdateDriveCacheSize();
 }
 
 }  // namespace options
 }  // namespace chromeos