src/vs/workbench/services/extensions/common/extensionHostManager.ts/ExtensionHostManager/_measureDown
class ExtensionHostManager:	private async _measureDown(proxy: IExtensionHostProxy): Promise<number> {
		const SIZE = 10 * 1024 * 1024; // 10MB

		const sw = StopWatch.create(true);
		await proxy.test_down(SIZE);
		sw.stop();
		return ExtensionHostManager._convert(SIZE, sw.elapsed());
	}