Examine source code of Comment Overlay

{
  "description": "Adds an overlay that rolls comments over the video",
  "manifest_version": 2,
  "name": "Comment Overlay",
  "version": "1.1",
  "icons": {
    "48": "icons/popup.png"
  },
  "permissions": [
    "activeTab",
    "storage",
    "*://*.bilibili.com/*",
    "*://*.acfun.cn/*",
    "*://*.aixifun.com/*"
  ],
  "browser_action": {
    "default_icon": "icons/popup.png",
    "theme_icons": [
      {
        "light": "icons/popup.png",
        "dark": "icons/popup.png",
        "size": 32
      }
    ],
    "default_title": "Comment Overlay",
    "default_popup": "popup/comment_overlay.html"
  }
}