Examine source code of Transparent Background

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Transparent",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(0, 0, 0, 0)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(26, 26, 26)",
      "tab_background_text": "rgb(182, 182, 182)",
      "toolbar_field": "rgba(3, 3, 3, 0.25)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgba(255, 255, 255, 0.25)",
      "popup": "rgb(37, 37, 37)",
      "popup_text": "rgb(255, 255, 255)",
      "tab_loading": "rgba(255, 255, 255, 0.25)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{9e467604-67d9-4c13-aa04-ba84736b8bbf}"
    }
  }
}