Examine source code of Measure Element

{
  "version": "1.1",
  "manifest_version": 2,
  "name": "__MSG_extensionName__",
  "description": "__MSG_extensionDescription__",
  "homepage_url": "https://devravik.github.io/aff/dn.json",
  "default_locale": "en",
  "icons": {
    "16": "icons/16.png",
    "32": "icons/32.png",
    "48": "icons/48.png",
    "64": "icons/64.png",
    "96": "icons/96.png",
    "128": "icons/128.png"
  },
  "browser_action": {
    "default_icon": "icons/128.png",
    "default_title": "__MSG_extensionName__"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "all_frames": false,
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_idle",
      "js": [
        "inject.js"
      ]
    }
  ],
  "permissions": [
    "*://*/*",
    "activeTab"
  ]
}