FileAPI: Factor out getting root URI and FS name parts into each FS backend

chrome/browser/chromeos/fileapi/file_system_backend.cc

 // Copyright 2013 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/chromeos/fileapi/file_system_backend.h"
 
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop.h"
 #include "base/path_service.h"
@@ skipping 95 matching lines @@
   }
 }
 
 void FileSystemBackend::OpenFileSystem(
     const GURL& origin_url,
     fileapi::FileSystemType type,
     fileapi::OpenFileSystemMode mode,
     const OpenFileSystemCallback& callback) {
   DCHECK(fileapi::IsolatedContext::IsIsolatedType(type));
   // Nothing to validate for external filesystem.
-  callback.Run(base::PLATFORM_FILE_OK);
+  callback.Run(GetFileSystemRootURI(origin_url, type),
+               GetFileSystemName(origin_url, type),
+               base::PLATFORM_FILE_OK);
 }
 
 fileapi::FileSystemQuotaUtil* FileSystemBackend::GetQuotaUtil() {
   // No quota support.
   return NULL;
 }
 
 bool FileSystemBackend::IsAccessAllowed(
     const fileapi::FileSystemURL& url) const {
   if (!url.is_valid())
@@ skipping 185 matching lines @@
   std::string mount_name = url.filesystem_id();
   if (!mount_points_->GetRegisteredPath(mount_name, &root_path) &&
       !system_mount_points_->GetRegisteredPath(mount_name, &root_path)) {
     return base::FilePath();
   }
 
   return root_path.DirName();
 }
 
 }  // namespace chromeos