Examine source code of Borderless Gray

{
  "manifest_version": 2,
  "version": "1.3",
  "name": "Borderless Gray",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-000-5672c42860d5b06e1058dc477397f3ef.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(28, 28, 28)",
      "toolbar_text": "rgb(170, 170, 170)",
      "frame": "rgb(28, 28, 28)",
      "tab_background_text": "rgb(170, 170, 170)",
      "toolbar_field": "rgb(51, 51, 51)",
      "toolbar_field_text": "rgb(205, 205, 205)",
      "tab_line": "rgba(255, 255, 255, 0)",
      "popup": "rgb(28, 28, 28)",
      "popup_text": "rgb(170, 170, 170)",
      "button_background_hover": "rgb(51, 51, 51)",
      "icons": "rgb(170, 170, 170)",
      "ntp_background": "rgb(28, 28, 28)",
      "popup_border": "rgba(205, 205, 205, 0)",
      "popup_highlight": "rgb(51, 51, 51)",
      "sidebar_border": "rgba(166, 166, 166, 0)",
      "sidebar_text": "rgb(170, 170, 170)",
      "sidebar": "rgb(28, 28, 28)",
      "tab_background_separator": "rgba(51, 51, 51, 0)",
      "tab_selected": "rgb(51, 51, 51)",
      "toolbar_bottom_separator": "rgba(0, 0, 0, 0)",
      "toolbar_field_border_focus": "rgba(255, 0, 0, 0)",
      "toolbar_field_border": "rgba(255, 0, 0, 0)",
      "toolbar_field_focus": "rgb(51, 51, 51)",
      "toolbar_field_highlight_text": "rgb(0, 0, 0)",
      "toolbar_field_highlight": "rgb(170, 170, 170)",
      "toolbar_field_separator": "rgba(28, 28, 28, 0)",
      "toolbar_top_separator": "rgba(43, 43, 43, 0)",
      "toolbar_vertical_separator": "rgba(28, 28, 28, 0)",
      "tab_loading": "rgba(255, 255, 255, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e02024db-f068-4668-842f-be179a393e84}"
    }
  }
}