YouTube.com fullscreen injection to put the video in fullscreen. (Scrubber disabled due to issues with the fullscreen mode)

youtube_fullscreen_injection.js

var sizeButton = document.getElementsByClassName("ytp-size-button")[0];
var sizeButtonTitle = sizeButton.getAttribute('title');
var shouldDefaultView = sizeButtonTitle != null && sizeButtonTitle.toLowerCase() == 'default view';

if (shouldDefaultView) {
    sizeButton.click();
}

setTimeout(function() {
    var playButton = document.getElementsByClassName("ytp-play-button")[0];
    var playButtonLabel = playButton.getAttribute('aria-label');
    var shouldPlay = playButtonLabel != null && playButtonLabel.toLowerCase() == 'pause';

    var moviePlayer = document.getElementById('movie_player');
    document.body.appendChild(moviePlayer);

    var elements = document.body.children;
    for (var i=elements.length-1; i>=0; i--)
    {
        var element = elements[i];
        if (element != moviePlayer) {
            element.parentNode.removeChild(element);
        }
    }

    (function() {
    var css = `
    body, html {
        height: 100% !important;
    }
    #movie_player, .html5-video-container, .video-stream {
        width: 100% !important;
        height: 100% !important;
    }
    .ytp-chrome-bottom {
        width: 100% !important;
        left: 0px !important;
    }
    .ytp-progress-bar-container {
        pointer-events: none;
    }
    `;
    var cssDiv = document.createElement('div'); cssDiv.innerHTML = '&shy;<style>' + css  + '</style>'; document.body.appendChild(cssDiv.childNodes[1]);
    })();

    if (shouldPlay) {
        setTimeout(function() { playButton.click(); }, 100);
    }
}, 100);