Add Transient FileSystem which goes away after its snapsot file is gone

webkit/fileapi/file_system_types.h

 // 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.
 
 #ifndef WEBKIT_FILEAPI_FILE_SYSTEM_TYPES_H_
 #define WEBKIT_FILEAPI_FILE_SYSTEM_TYPES_H_
 
 #include "third_party/WebKit/Source/Platform/chromium/public/WebFileSystem.h"
 #include "third_party/WebKit/Source/Platform/chromium/public/WebFileSystemType.h"
 
@@ skipping 68 matching lines @@
   // Indicates a Syncable sandboxed filesystem which can be backed by a
   // cloud storage service.
   kFileSystemTypeSyncable,
 
   // Indicates an external filesystem accessible by file paths from platform
   // Apps. As of writing, on non Chrome OS platform, this is merely a
   // kFileSystemTypeNativeLocal. On Chrome OS, the path is parsed by
   // the handlers of kFileSystemTypeExternal.
   kFileSystemTypeNativeForPlatformApp,
 
+  // Indicates an isolated filesystem which is supposed to contain one
+  // temporary which is supposed to go away when the last reference of
+  // its snapshot is dropped.
+  // This type is useful for creating a blob reference for a temporary
+  // file which must go away when the blob's last reference is dropped.
+  kFileSystemTypeForTransientFile,
+
   // --------------------------------------------------------------------
   // Marks the end of internal type enum. (This is not the actual fs type)
   // New internal filesystem types must be added above this line.
   kFileSystemInternalTypeEnumEnd,
 };
 
 }  // namespace fileapi
 
 #endif  // WEBKIT_FILEAPI_FILE_SYSTEM_TYPES_H_