Add an option to specify requested fields for fetching metadata.

storage/browser/fileapi/file_system_operation_impl.cc

Index: storage/browser/fileapi/file_system_operation_impl.cc
diff --git a/storage/browser/fileapi/file_system_operation_impl.cc b/storage/browser/fileapi/file_system_operation_impl.cc
index 79cf89e23d93b0664717e2b943bc5765dd91f9ef..b6a699778b920517e50c5798602195e8f55a0d33 100644
--- a/storage/browser/fileapi/file_system_operation_impl.cc
+++ b/storage/browser/fileapi/file_system_operation_impl.cc
@@ -131,7 +131,7 @@ void FileSystemOperationImpl::DirectoryExists(const FileSystemURL& url,
                                               const StatusCallback& callback) {
   DCHECK(SetPendingOperationType(kOperationDirectoryExists));
   async_file_util_->GetFileInfo(
-      operation_context_.Pass(), url,
+      operation_context_.Pass(), url, GET_METADATA_FIELD_IS_DIRECTORY,
       base::Bind(&FileSystemOperationImpl::DidDirectoryExists,
                  weak_factory_.GetWeakPtr(), callback));
 }
@@ -140,15 +140,17 @@ void FileSystemOperationImpl::FileExists(const FileSystemURL& url,
                                          const StatusCallback& callback) {
   DCHECK(SetPendingOperationType(kOperationFileExists));
   async_file_util_->GetFileInfo(
-      operation_context_.Pass(), url,
+      operation_context_.Pass(), url, GET_METADATA_FIELD_IS_DIRECTORY,
       base::Bind(&FileSystemOperationImpl::DidFileExists,
                  weak_factory_.GetWeakPtr(), callback));
 }
 
-void FileSystemOperationImpl::GetMetadata(
-    const FileSystemURL& url, const GetMetadataCallback& callback) {
+void FileSystemOperationImpl::GetMetadata(const FileSystemURL& url,
+                                          int fields,
+                                          const GetMetadataCallback& callback) {
   DCHECK(SetPendingOperationType(kOperationGetMetadata));
-  async_file_util_->GetFileInfo(operation_context_.Pass(), url, callback);
+  async_file_util_->GetFileInfo(operation_context_.Pass(), url, fields,
+                                callback);
 }
 
 void FileSystemOperationImpl::ReadDirectory(