src/vs/platform/extensionManagement/common/extensionManagementUtil.ts/ExtensionKey/create
class ExtensionKey:	static create(extension: IExtension | IGalleryExtension): ExtensionKey {
		const version = (extension as IExtension).manifest ? (extension as IExtension).manifest.version : (extension as IGalleryExtension).version;
		const targetPlatform = (extension as IExtension).manifest ? (extension as IExtension).targetPlatform : (extension as IGalleryExtension).properties.targetPlatform;
		return new ExtensionKey(extension.identifier, version, targetPlatform);
	}