Make audio players 100% wide in Chrome. https://chrome.google.com/webstore/detail/wide-audio-players/nhimhabjmplhihabgdijoeggnkalfkme

main.js

if (document.body.children.length == 1 && document.body.children[0].tagName == "VIDEO") {
  document.body.children[0].style.width = "100%";
}

manifest.json

{
  "name": "Wide audio players",
  "version": "1.0",
  "description": "Make audio players 100% wide.",
  "content_scripts": [
    {
      "matches": [
        "*://*/*.mp3*",
        "*://*/*.ogg*"
      ],
      "js": ["main.js"],
      "run_at": "document_end",
      "all_frames": true
    }
  ],
  "manifest_version": 2
}