src/vs/workbench/services/extensions/common/extensionDescriptionRegistry.ts/ExtensionDescriptionRegistry/_initialize
class ExtensionDescriptionRegistry:	private _initialize(): void {
		// Ensure extensions are stored in the order: builtin, user, under development
		this._extensionDescriptions.sort(extensionCmp);

		this._extensionsMap = new Map<string, IExtensionDescription>();
		this._extensionsArr = [];
		this._activationMap = new Map<string, IExtensionDescription[]>();

		for (const extensionDescription of this._extensionDescriptions) {
			if (this._extensionsMap.has(ExtensionIdentifier.toKey(extensionDescription.identifier))) {
				// No overwriting allowed!
				console.error('Extension `' + extensionDescription.identifier.value + '` is already registered');
				continue;
			}

			this._extensionsMap.set(ExtensionIdentifier.toKey(extensionDescription.identifier), extensionDescription);
			this._extensionsArr.push(extensionDescription);

			if (Array.isArray(extensionDescription.activationEvents)) {
				for (let activationEvent of extensionDescription.activationEvents) {
					// TODO@joao: there's no easy way to contribute this
					if (activationEvent === 'onUri') {
						activationEvent = `onUri:${ExtensionIdentifier.toKey(extensionDescription.identifier)}`;
					}

					if (!this._activationMap.has(activationEvent)) {
						this._activationMap.set(activationEvent, []);
					}
					this._activationMap.get(activationEvent)!.push(extensionDescription);
				}
			}
		}
	}