src/vs/workbench/services/extensions/common/extensionHostManager.ts/ExtensionHostManager/activateByEvent
class ExtensionHostManager:	public activateByEvent(activationEvent: string, activationKind: ActivationKind): Promise<void> {
		if (activationKind === ActivationKind.Immediate && !this._hasStarted) {
			return Promise.resolve();
		}

		if (!this._cachedActivationEvents.has(activationEvent)) {
			this._cachedActivationEvents.set(activationEvent, this._activateByEvent(activationEvent, activationKind));
		}
		return this._cachedActivationEvents.get(activationEvent)!;
	}