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) {
				trie.delete(await this._realPathExtensionUri(extensionDescription.extensionLocation));
			}
		}));

		await Promise.all(toAdd.map(async (extensionDescription) => {
			const realpathUri = await this._realPathExtensionUri(extensionDescription.extensionLocation);
			trie.set(realpathUri, extensionDescription);
		}));

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