Stream of progress events handled by this HttpRequestEventTarget.
Source
@DomName('XMLHttpRequestEventTarget.onprogress')
@DocsEditable()
@SupportedBrowser(SupportedBrowser.CHROME)
@SupportedBrowser(SupportedBrowser.FIREFOX)
@SupportedBrowser(SupportedBrowser.IE, '10')
@SupportedBrowser(SupportedBrowser.SAFARI)
@Experimental() // untriaged
Stream<ProgressEvent> get onProgress => progressEvent.forTarget(this);