src/vs/editor/browser/viewParts/overviewRuler/overviewRuler.ts/OverviewRuler/_render
class OverviewRuler:	private _render(): boolean {
		if (this._zoneManager.getOuterHeight() === 0) {
			return false;
		}

		const width = this._zoneManager.getCanvasWidth();
		const height = this._zoneManager.getCanvasHeight();

		const colorZones = this._zoneManager.resolveColorZones();
		const id2Color = this._zoneManager.getId2Color();

		const ctx = this._domNode.domNode.getContext('2d')!;
		ctx.clearRect(0, 0, width, height);
		if (colorZones.length > 0) {
			this._renderOneLane(ctx, colorZones, id2Color, width);
		}

		return true;
	}