src/vs/platform/undoRedo/common/undoRedoService.ts/WorkspaceStackElement/removeResource
class WorkspaceStackElement:	public removeResource(resourceLabel: string, strResource: string, reason: RemovedResourceReason): void {
		if (!this.removedResources) {
			this.removedResources = new RemovedResources();
		}
		if (!this.removedResources.has(strResource)) {
			this.removedResources.set(strResource, new ResourceReasonPair(resourceLabel, reason));
		}
	}