Examine source code of Split-Level 1.0

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#c9c9c9",
      "tab_background_text": "#333333"
    }
  },
  "version": "2.0",
  "name": "Split-Level 1.0",
  "manifest_version": 2,
  "description": "Very simple, split level header, light grey theme. Looks best with menu and navigation and without bookmarks toolbar, but works with it too."
}