Examine source code of Transparent Gradient

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Transparent Gradient",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "right top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(56, 56, 56, 0.5)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(0, 0, 0)",
      "tab_background_text": "rgb(192, 192, 192)",
      "toolbar_field": "rgba(45, 36, 45, 0.95)",
      "toolbar_field_text": "rgb(192, 159, 134)",
      "tab_line": "rgba(255, 255, 255, 0)",
      "popup": "rgba(45, 36, 45, 0.9)",
      "popup_text": "rgb(160, 160, 160)",
      "tab_loading": "rgba(255, 255, 255, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{996b5d9c-5a3e-4cb4-9ce6-a73c305788f5}"
    }
  }
}