Examine source code of Mail Activity Indicator

{
  "version": "0.2.0",
  "manifest_version": 2,
  "name": "__MSG_extensionName__",
  "short_name": "__MSG_extensionName__",
  "description": "__MSG_extensionDescription__",
  "options_ui": {
    "open_in_tab": true,
    "page": "data/options/options.html"
  },
  "permissions": [
    "alarms",
    "storage",
    "webRequest",
    "notifications",
    "*://*.gmx.com/*",
    "*://*.live.com/*",
    "*://*.mail.com/*",
    "*://*.yahoo.com/*",
    "*://*.icloud.com/*",
    "*://mail.google.com/*",
    "webRequestBlocking"
  ],
  "background": {
    "scripts": [
      "lib/emails/gmx.js",
      "lib/emails/live.js",
      "lib/emails/yahoo.js",
      "lib/emails/gmail.js",
      "lib/emails/icloud.js",
      "lib/emails/mailcom.js",
      "lib/config.js",
      "lib/chrome.js",
      "lib/runtime.js",
      "lib/common.js"
    ]
  },
  "browser_action": {
    "default_title": "__MSG_extensionName__",
    "default_popup": "data/popup/popup.html",
    "default_icon": {
      "16": "data/icons/16.png",
      "32": "data/icons/32.png",
      "48": "data/icons/48.png",
      "64": "data/icons/64.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c2d5f8a2-6b2d-5e9a-8f9d-5b0a15dcf5cd}",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "collects_data": false
      }
    }
  },
  "content_scripts": [
    {
      "all_frames": true,
      "run_at": "document_start",
      "js": [
        "data/content_script/inject.js"
      ],
      "matches": [
        "*://*.gmx.com/*",
        "*://*.mail.com/*"
      ]
    }
  ],
  "icons": {
    "16": "data/icons/16.png",
    "32": "data/icons/32.png",
    "48": "data/icons/48.png",
    "64": "data/icons/64.png",
    "128": "data/icons/128.png"
  }
}