YouTube Mobile Fullscreen Fix for Kiwi Browser

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// ==UserScript==
// @name:ko           키위브라우저 유튜브 풀스크린 잘림 개선
// @name              YouTube Mobile Fullscreen Fix for Kiwi Browser

// @description:ko    -
// @description	      -

// @namespace         https://ndaesik.tistory.com/
// @version           1.0
// @author            ndaesik
// @icon              https://t1.gstatic.com/faviconV2?client=SOCIAL&type=FAVICON&fallback_opts=TYPE,SIZE,URL&url=https://www.youtube.com
// @match             *://*.youtube.com/*
// ==/UserScript==

(function() {
    const FIREFOX_UA = 'Mozilla/5.0 (Windows Phone 10.0; Android 8.0.0; Microsoft; Lumia 950XL) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.75 Mobile Safari/537.36 Edge/15.15063';
    const setUserAgent = () => {
        if (window.location.hostname.includes('youtube.com')) {
            Object.defineProperty(navigator, 'userAgent', { get: () => FIREFOX_UA });
            Object.defineProperty(navigator, 'platform', { get: () => 'Windows Phone' });
        }
    };
    setUserAgent();
    new MutationObserver(setUserAgent).observe(document.documentElement, { childList: true, subtree: true });
})();