src/vs/base/browser/browser.ts/PixelRatioImpl/constructor
class PixelRatioImpl:	constructor() {
		super();

		this._value = this._getPixelRatio();

		const dprMonitor = this._register(new DevicePixelRatioMonitor());
		this._register(dprMonitor.onDidChange(() => {
			this._value = this._getPixelRatio();
			this._onDidChange.fire(this._value);
		}));
	}