Version: ToT
OS: Linux

1. launch Chrome with a fresh --user-data-dir

Note that the frame matches desktop theme theme (is black, for me)

2. navigate to chrome://md-settings

Expected: "Reset to Default" button next to Appearance > Theme is hidden.
Actual: "Reset to Default" button is available.

3. tap "Reset to Default"

Expected: nothing, because this is already the default by definition
Actual: my frame becomes light grey, and the "Reset to Default" button gets hidden

Looking in chrome://settings-frame, it looks like the "Reset to Default" button is changing to the Classic theme, when the default apparently was the GTK+ theme.