src/vs/workbench/api/common/extHostExtensionActivator.ts/ExtensionsActivator/constructor
class ExtensionsActivator:	constructor(
		registry: ExtensionDescriptionRegistry,
		resolvedExtensions: ExtensionIdentifier[],
		externalExtensions: ExtensionIdentifier[],
		host: IExtensionsActivatorHost,
		@ILogService private readonly _logService: ILogService
	) {
		this._registry = registry;
		this._resolvedExtensionsSet = new Set<string>();
		resolvedExtensions.forEach((extensionId) => this._resolvedExtensionsSet.add(ExtensionIdentifier.toKey(extensionId)));
		this._externalExtensionsMap = new Map<string, ExtensionIdentifier>();
		externalExtensions.forEach((extensionId) => this._externalExtensionsMap.set(ExtensionIdentifier.toKey(extensionId), extensionId));
		this._host = host;
		this._operations = new Map<string, ActivationOperation>();
		this._alreadyActivatedEvents = Object.create(null);
	}