src/vs/base/browser/fastDomNode.ts/FastDomNode/setLetterSpacing
class FastDomNode:	public setLetterSpacing(_letterSpacing: number | string): void {
		const letterSpacing = numberAsPixels(_letterSpacing);
		if (this._letterSpacing === letterSpacing) {
			return;
		}
		this._letterSpacing = letterSpacing;
		this.domNode.style.letterSpacing = this._letterSpacing;
	}