Examine source code of Metallic sound

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Metallic sound",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(225, 225, 225, 0.25)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(104, 108, 113)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(242, 242, 242)",
      "toolbar_field_text": "rgb(32, 105, 133)",
      "tab_line": "rgb(234, 213, 124)",
      "popup": "rgb(213, 211, 231)",
      "popup_text": "rgb(0, 0, 0)",
      "ntp_background": "rgb(219, 225, 233)",
      "ntp_text": "rgb(0, 0, 0)",
      "popup_border": "rgb(199, 124, 55)",
      "tab_loading": "rgb(234, 213, 124)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{f4391513-d643-453f-9c23-1d7c25d4e3f1}"
    }
  }
}