Examine source code of Drag Scroll

{
  "manifest_version": 2,
  "name": "Drag Scroll",
  "description": "Scroll the page and elements by dragging like on a tablet or smartphone",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png",
    "128": "icons/icon-128.png",
    "256": "icons/icon-256.png"
  },
  "version": "0.2.1resigned1",
  "content_scripts": [
    {
      "matches": [
        "*://*/*",
        "http://*/*",
        "https://*/*",
        "ftp://*/*",
        "file://*/*"
      ],
      "js": [
        "DragScroll.js",
        "dsapp.js"
      ],
      "run_at": "document_start",
      "all_frames": true
    }
  ],
  "background": {
    "scripts": []
  },
  "browser_action": {
    "default_icon": "icons/icon-32.png",
    "default_popup": "popup.html"
  },
  "permissions": [
    "activeTab",
    "storage",
    "http://*/*",
    "https://*/*",
    "ftp://*/*",
    "file://*/*"
  ],
  "applications": {
    "gecko": {
      "id": "{96bec0f4-e8b0-487d-97dc-09197dab4340}"
    }
  }
}