src/vs/workbench/services/views/browser/viewDescriptorService.ts/ViewDescriptorService/onDidChangeActiveViews
class ViewDescriptorService:	private onDidChangeActiveViews({ added, removed }: { added: ReadonlyArray<IViewDescriptor>, removed: ReadonlyArray<IViewDescriptor>; }): void {
		this.contextKeyService.bufferChangeEvents(() => {
			added.forEach(viewDescriptor => this.getOrCreateActiveViewContextKey(viewDescriptor).set(true));
			removed.forEach(viewDescriptor => this.getOrCreateActiveViewContextKey(viewDescriptor).set(false));
		});
	}