Examine source code of Dev Toolbox

{
  "name" : "Dev Toolbox",
  "description" : "Dev Toolbox provides quick offline access to various development tools.",
  "version" : "1.1.8",
  "manifest_version" : 2 ,
  "permissions" : [
    "storage" 
  ],
  "browser_action" : {
    "default_popup" : "index.html",
    "default_icon" : {
      "16" : "/img/tb_16.png",
      "24" : "/img/tb_24.png"
    }
  },
  "icons" : {
    "16" : "/img/tb_16.png",
    "24" : "/img/tb_24.png",
    "32" : "/img/tb_32.png",
    "48" : "/img/tb_48.png",
    "128" : "/img/tb_128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{37ac6010-f513-4f04-a96f-aa22b34d386f}"
    }
  }
}