src/vs/editor/standalone/browser/standaloneServices.ts/initialize
	export function initialize(overrides: IEditorOverrideServices): IInstantiationService {
		if (initialized) {
			return instantiationService;
		}
		initialized = true;

		// Add singletons that were registered after this module loaded
		for (const [id, descriptor] of getSingletonServiceDescriptors()) {
			if (!serviceCollection.get(id)) {
				serviceCollection.set(id, descriptor);
			}
		}

		// Initialize the service collection with the overrides, but only if the
		// service was not instantiated in the meantime.
		for (const serviceId in overrides) {
			if (overrides.hasOwnProperty(serviceId)) {
				const serviceIdentifier = createDecorator(serviceId);
				const r = serviceCollection.get(serviceIdentifier);
				if (r instanceof SyncDescriptor) {
					serviceCollection.set(serviceIdentifier, overrides[serviceId]);
				}
			}
		}

		return instantiationService;
	}