src/vs/workbench/api/common/extHostExtensionService.ts/AbstractExtHostExtensionService/$deltaExtensions
class AbstractExtHostExtensionService:	public async $deltaExtensions(toAdd: IExtensionDescription[], toRemove: ExtensionIdentifier[]): Promise<void> {
		toAdd.forEach((extension) => (<any>extension).extensionLocation = URI.revive(extension.extensionLocation));

		const trie = await this.getExtensionPathIndex();

		await Promise.all(toRemove.map(async (extensionId) => {
			const extensionDescription = this._registry.getExtensionDescription(extensionId);
			if (!extensionDescription) {
				return;
			}
			const realpathValue = await this._hostUtils.realpath(extensionDescription.extensionLocation.fsPath);
			trie.delete(URI.file(realpathValue).fsPath);
		}));

		await Promise.all(toAdd.map(async (extensionDescription) => {
			const realpathValue = await this._hostUtils.realpath(extensionDescription.extensionLocation.fsPath);
			trie.set(URI.file(realpathValue).fsPath, extensionDescription);
		}));

		this._registry.deltaExtensions(toAdd, toRemove);
		return Promise.resolve(undefined);
	}