JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <iframe src="http://www.youtube.com/embed/QKh1Rv0PlOQ?rel=0&showinfo=0&autohide=1&wmode=transparent" frameborder="0" allowfullscreen>
    </iframe>
    <div class="corner topleft"></div>
    <div class="corner topright"></div>
    <div class="corner bottomright"></div>
    <div class="corner bottomleft"></div>
</div>

CSS

.container {
    position: relative;
    max-width: 480px;
    height:360px;
}

.corner {
    background: url(http://i40.tinypic.com/tak7dt.png) no-repeat top left;
    height: 10px;
    position: absolute;
    width: 10px;
    z-index: 99;
}

.topleft {
    left: 0;
    top: 0;
}

.topright {
    right: 0;
    top: 0;
    -moz-transform: rotate(90deg);
    -ms-transform: rotate(90deg);
    -o-transform: rotate(90deg);
    -webkit-transform: rotate(90deg);
}

.bottomright {
    bottom: 0;
    right: 0;
    -moz-transform: rotate(180deg);
    -ms-transform: rotate(180deg);
    -o-transform: rotate(180deg);
    -webkit-transform: rotate(180deg);
}

.bottomleft {
    bottom: 0;
    left: 0;
    -moz-transform: rotate(270deg);
    -ms-transform: rotate(270deg);
    -o-transform: rotate(270deg);
    -webkit-transform: rotate(270deg);
}

iframe {
    width: 100%;
    height: 100%;
}