Examine source code of Dimensions

{
  "name": "Dimensions",
  "description": "A tool for designers to measure screen dimensions",
  "version": "2.1.1resigned1",
  "manifest_version": 2,
  "author": "Felix Niklas",
  "icons": {
    "16": "images/icon16.png",
    "32": "images/icon16@2x.png",
    "48": "images/icon48.png",
    "128": "images/icon128.png"
  },
  "background": {
    "scripts": [
      "chrome.js"
    ],
    "persistent": false
  },
  "commands": {
    "_execute_browser_action": {
      "suggested_key": {
        "default": "Alt+D"
      }
    }
  },
  "browser_action": {
    "default_icon": {
      "16": "images/icon16.png",
      "19": "images/icon19.png",
      "32": "images/icon16@2x.png",
      "38": "images/icon19@2x.png"
    },
    "default_title": "Measure Dimensions"
  },
  "permissions": [
    "activeTab",
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{38300720-a4e6-4463-a5d4-d3e981959f59}"
    }
  }
}