SyncFS: Add resource type field into DriveMetadata

chrome/browser/sync_file_system/sync_file_system.proto

Index: chrome/browser/sync_file_system/sync_file_system.proto
diff --git a/chrome/browser/sync_file_system/sync_file_system.proto b/chrome/browser/sync_file_system/sync_file_system.proto
index 8d99f6f1bb0e6204a821bd2636b17cb9cddfc9f1..53820463cbcf26f619e30bb517eda2ee63c1ba9c 100644
--- a/chrome/browser/sync_file_system/sync_file_system.proto
+++ b/chrome/browser/sync_file_system/sync_file_system.proto
@@ -18,4 +18,11 @@ message DriveMetadata {
   // When true, indicates that the remote file identified by |resource_id|
   // should be fetched for solving the conflict (resolve-to-remote resolution).
   required bool to_be_fetched = 4;
+
+  enum ResourceType {
+    RESOURCE_TYPE_FILE = 0;
+    RESOURCE_TYPE_FOLDER = 1;
+  }
+
+  optional ResourceType type = 5 [default = RESOURCE_TYPE_FILE];
 }