Disable package selection for multiple-selection file dialogs.

ui/shell_dialogs/select_file_dialog_mac.mm

Index: ui/shell_dialogs/select_file_dialog_mac.mm
diff --git a/ui/shell_dialogs/select_file_dialog_mac.mm b/ui/shell_dialogs/select_file_dialog_mac.mm
index 168ef1da1505ca6445778e585dee5e7311dd6590..78d829da2a32979f53c49c789e01a86d9b592c8e 100644
--- a/ui/shell_dialogs/select_file_dialog_mac.mm
+++ b/ui/shell_dialogs/select_file_dialog_mac.mm
@@ -161,8 +161,9 @@ void SelectFileDialogImpl::FileWasSelected(
 
 bool SelectFileDialogImpl::ShouldEnableFilename(NSSavePanel* dialog,
                                                 NSString* filename) {
-  // If this is a single open file dialog, disable selecting packages.
-  if (type_map_[dialog] != SELECT_OPEN_FILE)
+  // If this is a single/multiple open file dialog, disable selecting packages.
+  if (type_map_[dialog] != SELECT_OPEN_FILE &&
+      type_map_[dialog] != SELECT_OPEN_MULTI_FILE)
     return true;
 
   return ![[NSWorkspace sharedWorkspace] isFilePackageAtPath:filename];