::shadow selector is deprecatiated

[zvodd]

See

• https://www.chromestatus.com/feature/6750456638341120
• https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/68qSZM5QMRQ/pT2YCqZSomAJ

Might need to patch in the styles by moving all the ::shadow css into another file and removing the preceding XXX::shadow selector, then loading the stylesheet into shadow dom.
i.e. something like:

var eStyle = document.createElement("link");
eStyle.href = chrome.runtime.getURL("./shadow_style.css");
document.querySelector(".sophis-video-control").shadowRoot.appendChild(eStyle);