[fsp] Add support for providing thumbnails.

chrome/browser/chromeos/file_system_provider/provided_file_system.cc

 // Copyright 2014 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/file_system_provider/provided_file_system.h"
 
 #include <vector>
 
 #include "base/debug/trace_event.h"
 #include "base/files/file.h"
@@ skipping 60 matching lines @@
     callback.Run(base::File::FILE_ERROR_SECURITY);
     return AbortCallback();
   }
 
   return base::Bind(
       &ProvidedFileSystem::Abort, weak_ptr_factory_.GetWeakPtr(), request_id);
 }
 
 ProvidedFileSystem::AbortCallback ProvidedFileSystem::GetMetadata(
     const base::FilePath& entry_path,
+    MetadataFieldMask fields,
     const GetMetadataCallback& callback) {
   const int request_id = request_manager_.CreateRequest(
       GET_METADATA,
       scoped_ptr<RequestManager::HandlerInterface>(new operations::GetMetadata(
-          event_router_, file_system_info_, entry_path, callback)));
+          event_router_, file_system_info_, entry_path, fields, callback)));
   if (!request_id) {
-    callback.Run(EntryMetadata(), base::File::FILE_ERROR_SECURITY);
+    callback.Run(make_scoped_ptr<EntryMetadata>(NULL),
+                 base::File::FILE_ERROR_SECURITY);
     return AbortCallback();
   }
 
   return base::Bind(
       &ProvidedFileSystem::Abort, weak_ptr_factory_.GetWeakPtr(), request_id);
 }
 
 ProvidedFileSystem::AbortCallback ProvidedFileSystem::ReadDirectory(
     const base::FilePath& directory_path,
     const storage::AsyncFileUtil::ReadDirectoryCallback& callback) {
@@ skipping 243 matching lines @@
               new operations::Abort(event_router_,
                                     file_system_info_,
                                     operation_request_id,
                                     callback)))) {
     callback.Run(base::File::FILE_ERROR_SECURITY);
   }
 }
 
 }  // namespace file_system_provider
 }  // namespace chromeos