Examine source code of Pulse SMS Extension

{
  "manifest_version": 2,
  "name": "Pulse SMS Extension",
  "description": "Text message your friends from your computer",
  "version": "2.1.4",
  "browser_action": {
    "default_icon": "assets/icon_48.png",
    "default_popup": "popup.html",
    "default_title": "Pulse SMS"
  },
  "minimum_chrome_version": "38",
  "permissions": [
    "storage",
    "tabs",
    "gcm",
    "notifications",
    "background"
  ],
  "icons": {
    "16": "assets/icon_16.png",
    "48": "assets/icon_48.png",
    "96": "assets/icon_96.png",
    "128": "assets/icon_128.png",
    "256": "assets/icon_256.png"
  },
  "background": {
    "scripts": [
      "sjcl.js",
      "hmacsha1.js",
      "messenger.js"
    ]
  },
  "externally_connectable": {
    "matches": [
      "https://pulsesms.app/*"
    ]
  },
  "author": "Luke Klinker",
  "options_ui": {
    "page": "options.html",
    "chrome_style": true
  }
}