src/vs/platform/markers/common/markerService.ts/MarkerStats/_update
class MarkerStats:	private _update(resources: readonly URI[]): void {
		for (const resource of resources) {
			const oldStats = this._data.get(resource);
			if (oldStats) {
				this._substract(oldStats);
			}
			const newStats = this._resourceStats(resource);
			this._add(newStats);
			this._data.set(resource, newStats);
		}
	}