Make isolated file system works for a device root (e.g. X:\\)

chrome/browser/extensions/api/media_gallery/media_gallery_api.cc

 // Copyright (c) 2012 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.
 
 // Implements the Chrome Extensions Media Galleries API.
 
 #include "chrome/browser/extensions/api/media_gallery/media_gallery_api.h"
 
 #include <string>
 #include <vector>
@@ skipping 25 matching lines @@
 
   const int child_id = rph->GetID();
   base::ListValue* list = new base::ListValue();
   for (size_t i = 0; i < filesystems.size(); i++) {
     // TODO(thestig) Check permissions to file systems when that capability
     // exists.
     const MediaFileSystemRegistry::MediaFSIDAndPath& fsid_and_path =
         filesystems[i];
     const std::string& fsid = fsid_and_path.first;
     const FilePath& path = fsid_and_path.second;
-    const std::string basepath_utf8(path.BaseName().AsUTF8Unsafe());
 
     base::DictionaryValue* dict_value = new base::DictionaryValue();
     dict_value->SetWithoutPathExpansion(
         "fsid", Value::CreateStringValue(fsid));
+    // The directory name is not exposed to the js layer.
     dict_value->SetWithoutPathExpansion(
-        "dirname", Value::CreateStringValue(basepath_utf8));
+        "dirname", Value::CreateStringValue("_"));
     list->Append(dict_value);
 
     content::ChildProcessSecurityPolicy* policy =
         ChildProcessSecurityPolicy::GetInstance();
     if (!policy->CanReadFile(child_id, path))
       policy->GrantReadFile(child_id, path);
     policy->GrantReadFileSystem(child_id, fsid);
   }
 
   result_.reset(list);
@@ skipping 10 matching lines @@
 
 AssembleMediaFileFunction::~AssembleMediaFileFunction() {}
 
 bool AssembleMediaFileFunction::RunImpl() {
   // TODO(vandebo) Update the metadata and return the new file.
   result_.reset(Value::CreateNullValue());
   return true;
 }
 
 }  // namespace extensions