src/vs/workbench/services/extensions/common/extensionsRegistry.ts/ExtensionsRegistryImpl/registerExtensionPoint
class ExtensionsRegistryImpl:	public registerExtensionPoint<T>(desc: IExtensionPointDescriptor): IExtensionPoint<T> {
		if (this._extensionPoints.has(desc.extensionPoint)) {
			throw new Error('Duplicate extension point: ' + desc.extensionPoint);
		}
		const result = new ExtensionPoint<T>(desc.extensionPoint, desc.defaultExtensionKind);
		this._extensionPoints.set(desc.extensionPoint, result);

		schema.properties!['contributes'].properties![desc.extensionPoint] = desc.jsonSchema;
		schemaRegistry.registerSchema(schemaId, schema);

		return result;
	}