Examine source code of Last Tabs

{
  "manifest_version": 2,
  "description": "Provides a menu with your previous tabs in order of access - never loose track of you last tab again!",
  "name": "Last Tabs",
  "browser_action": {
    "default_icon": "img/icon19.png",
    "default_title": "LASTabs",
    "default_popup": "popup.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_page": "options.html",
  "commands": {
    "navigate-last-tab-1": {
      "suggested_key": {
        "default": "Alt+Shift+1",
        "mac": "Command+Shift+1"
      },
      "description": "Take me to the last tab I was on"
    },
    "navigate-last-tab-2": {
      "suggested_key": {
        "default": "Alt+Shift+2",
        "mac": "Command+Shift+2"
      },
      "description": "Take me two tabs back"
    },
    "navigate-last-tab-3": {
      "suggested_key": {
        "default": "Alt+Shift+3",
        "mac": "Command+Shift+5"
      },
      "description": "Take me three tabs back"
    }
  },
  "icons": {
    "16": "img/icon16.png",
    "32": "img/icon32.png",
    "48": "img/icon48.png",
    "128": "img/icon128.png"
  },
  "permissions": [
    "<all_urls>",
    "tabs"
  ],
  "version": "0.0.4.11resigned1",
  "browser_specific_settings": {
    "gecko": {
      "id": "{3091e8bb-90cf-4472-a6f0-f01a9ca69d0e}"
    }
  }
}