[fsp] Add support for providing thumbnails.

chrome/browser/chromeos/file_system_provider/provided_file_system.cc

Index: chrome/browser/chromeos/file_system_provider/provided_file_system.cc
diff --git a/chrome/browser/chromeos/file_system_provider/provided_file_system.cc b/chrome/browser/chromeos/file_system_provider/provided_file_system.cc
index dc0de56cdd8ca66d50f72651331febe7da716ced..9f8450cb2f7995f40bd06eb89ef7bb72c3ad0829 100644
--- a/chrome/browser/chromeos/file_system_provider/provided_file_system.cc
+++ b/chrome/browser/chromeos/file_system_provider/provided_file_system.cc
@@ -78,13 +78,15 @@ ProvidedFileSystem::AbortCallback ProvidedFileSystem::RequestUnmount(
 
 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();
   }