Examine source code of PageTimer

{
  "manifest_version": 2,
  "name": "PageTimer",
  "version": "0.1.1resigned1",
  "description": "PageTimer is an extension for Firefox that measures page loading time.",
  "homepage_url": "https://github.com/DeliciousGarfield/PageTimer",
  "icons": {
    "48": "icons/icon.png"
  },
  "applications": {
    "gecko": {
      "id": "pagetimer@tianxiduo.org"
    }
  },
  "permissions": [
    "tabs"
  ],
  "page_action": {
    "default_icon": "icons/icon.png",
    "default_title": "Page Timer"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content_script.js"
      ]
    }
  ]
}