Examine source code of 140chars

{
  "manifest_version": 2,
  "name": "140chars",
  "version": "1.2resigned1",
  "description": "Filter out all twits with more than 140 chars",
  "icons": {
    "32": "icons/140chars-32.png",
    "48": "icons/140chars-48.png",
    "96": "icons/140chars-96.png"
  },
  "browser_action": {
    "default_icon": "icons/140chars-32.png",
    "default_title": "140 chars",
    "default_popup": "popup/options.html"
  },
  "background": {
    "persistent": false,
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.twitter.com/*"
      ],
      "js": [
        "140chars.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{5fc96704-f764-48a2-834c-6f33a1359ac5}"
    }
  }
}