Add an option to specify requested fields for fetching metadata.

storage/browser/fileapi/file_system_operation.h

Index: storage/browser/fileapi/file_system_operation.h
diff --git a/storage/browser/fileapi/file_system_operation.h b/storage/browser/fileapi/file_system_operation.h
index b9e6f95cf26c7829276f63e72a8319a86ad94908..8580b351be24a512868ec84a07fbbfb2653a1fab 100644
--- a/storage/browser/fileapi/file_system_operation.h
+++ b/storage/browser/fileapi/file_system_operation.h
@@ -227,6 +227,14 @@ class FileSystemOperation {
     OPTION_PRESERVE_LAST_MODIFIED,
   };
 
+  // Fields requested for the GetMetadata method. Used as a bitmask.
+  enum GetMetadataField {
+    GET_METADATA_FIELD_NONE = 0,
+    GET_METADATA_FIELD_SIZE = 1 << 0,
+    GET_METADATA_FIELD_IS_DIRECTORY = 1 << 1,
+    GET_METADATA_FIELD_LAST_MODIFIED = 1 << 2
+  };
+
   // Used for Write().
   typedef base::Callback<void(base::File::Error result,
                               int64 bytes,
@@ -302,6 +310,7 @@ class FileSystemOperation {
 
   // Gets the metadata of a file or directory at |path|.
   virtual void GetMetadata(const FileSystemURL& path,
+                           int fields,
                            const GetMetadataCallback& callback) = 0;
 
   // Reads contents of a directory at |path|.