src/vs/editor/browser/controller/textAreaInput.ts/TextAreaWrapper/hasFocus
class TextAreaWrapper:	public hasFocus(): boolean {
		const shadowRoot = dom.getShadowRoot(this._actual);
		if (shadowRoot) {
			return shadowRoot.activeElement === this._actual;
		} else if (dom.isInDOM(this._actual)) {
			return document.activeElement === this._actual;
		} else {
			return false;
		}
	}