Examine source code of Time Speaks

{
  "name": "Time Speaks",
  "version": "1.2.1resigned1",
  "manifest_version": 2,
  "description": "Shows the runtime of the active tab",
  "permissions": [
    "tabs",
    "history",
    "storage"
  ],
  "applications": {
    "gecko": {
      "id": "timespeaks@shipra.addons.mozilla.org"
    }
  },
  "web_accessible_resources": [
    "pages/more.html"
  ],
  "background": {
    "scripts": [
      "background/background.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "16": "images/icon16.png",
      "48": "images/icon48.png",
      "128": "images/icon128.png"
    },
    "default_popup": "pages/popup.html"
  },
  "icons": {
    "16": "images/icon16.png",
    "48": "images/icon48.png",
    "128": "images/icon128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "core/content.js"
      ]
    }
  ]
}