Examine source code of Gaintime Main Extension

{
  "name": "Gaintime Main Extension",
  "description": "Extension showing use of the InboxSDK adding action items from Gmail",
  "icons": {
    "16": "favicon.png",
    "48": "favicon48.png"
  },
  "version": "1.0",
  "content_scripts": [
    {
      "matches": [
        "https://mail.google.com/*",
        "https://inbox.google.com/*",
        "https://www.mozilla.org/en-US/firefox/new/*"
      ],
      "js": [
        "inboxsdk.js",
        "content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "web_accessible_resources": [
    "favicon.png"
  ],
  "permissions": [
    "https://mail.google.com/",
    "https://inbox.google.com/"
  ],
  "manifest_version": 2,
  "browser_specific_settings": {
    "gecko": {
      "id": "{31222a71-1d87-45c1-8b2f-b7f37e112140}"
    }
  }
}