Examine source code of Sen - For Tree Style Tabs

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Sen",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(14, 2, 5, 0.92)",
      "toolbar_text": "rgb(255, 217, 217)",
      "frame": "rgb(14, 2, 5)",
      "tab_background_text": "rgb(255, 217, 217)",
      "toolbar_field": "rgba(255, 255, 255, 0.15)",
      "toolbar_field_text": "rgb(255, 217, 217)",
      "tab_line": "rgb(255, 129, 131)",
      "popup": "rgb(14, 2, 5)",
      "popup_text": "rgb(255, 216, 216)",
      "button_background_active": "rgb(255, 232, 232)",
      "icons_attention": "rgb(255, 217, 217)",
      "sidebar_highlight": "rgb(255, 217, 217)",
      "tab_background_separator": "rgb(255, 217, 217)",
      "tab_loading": "rgb(255, 217, 217)",
      "toolbar_field_border": "rgb(255, 217, 217)",
      "toolbar_field_highlight_text": "rgb(255, 217, 217)",
      "toolbar_field_separator": "rgb(255, 217, 217)",
      "toolbar_vertical_separator": "rgb(255, 217, 217)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{4ca6cd5a-7944-44b2-bd03-cf2f299f401d}"
    }
  }
}