Chrome tab counter

manifest.json

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 2,
  "name": "Chrome tab counter",
  "short_name": "Tab counter",
  "description": "This extension shows the total number of tabs.  Click on the icon to see the number of tabs inside the current window.",
  "version": "0.1",
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html",
    "default_title": "Number of tabs"
  },
  "permissions": [
    "tabs",
    "https://ajax.googleapis.com/"
  ],
  "content_scripts": [
    {
      "js": [
        "popup.js"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ],
  "background": {
    "scripts": [
      "eventPage.js"
    ],
    "persistent": false
  }
}