revert 8a2a9ead92

revert [gtk] Default the file dialog operation to cancelling the operation.

While this could be an annoying default for users expecting fast-track
dialog operations with hitting enter, it avoids potential social
engineering attacks and unintended file operations.

widget/gtk/nsFilePicker.cpp

@@ -465,9 +465,8 @@ nsFilePicker::Open(nsIFilePickerShownCallback *aCallback)
     }
   }
 
-  // Default to cancelling the operation.
   if (GTK_IS_DIALOG(file_chooser)) {
-    gtk_dialog_set_default_response(GTK_DIALOG(file_chooser), GTK_RESPONSE_CANCEL);
+    gtk_dialog_set_default_response(GTK_DIALOG(file_chooser), GTK_RESPONSE_ACCEPT);
   }
 
   int32_t count = mFilters.Length();