See bug 1552325 comment 0.

Here is an example of such event:

{"method":"Network.responseReceived","params":{"requestId":"F931C3A196EED24B5886CF5D1842D29E","loaderId":"F931C3A196EED24B5886CF5D1842D29E","timestamp":68261.802608,"type":"Document","response":{"url":"http://localhost:8889/wp-admin/post-new.php","status":200,"statusText":"OK","headers":{"Date":"Thu, 16 May 2019 18:02:36 GMT","Server":"Apache/2.4.25 (Debian)","X-Powered-By":"PHP/7.2.18","Expires":"Wed, 11 Jan 1984 05:00:00 GMT","Cache-Control":"no-cache, must-revalidate, max-age=0","X-Frame-Options":"SAMEORIGIN","Referrer-Policy":"strict-origin-when-cross-origin","Vary":"Accept-Encoding","Content-Encoding":"gzip","Content-Length":"51673","Keep-Alive":"timeout=5, max=79","Connection":"Keep-Alive","Content-Type":"text/html; charset=UTF-8"},"headersText":"HTTP/1.1 200 OK\r\nDate: Thu, 16 May 2019 18:02:36 GMT\r\nServer: Apache/2.4.25 (Debian)\r\nX-Powered-By: PHP/7.2.18\r\nExpires: Wed, 11 Jan 1984 05:00:00 GMT\r\nCache-Control: no-cache, must-revalidate, max-age=0\r\nX-Frame-Options: SAMEORIGIN\r\nReferrer-Policy: strict-origin-when-cross-origin\r\nVary: Accept-Encoding\r\nContent-Encoding: gzip\r\nContent-Length: 51673\r\nKeep-Alive: timeout=5, max=79\r\nConnection: Keep-Alive\r\nContent-Type: text/html; charset=UTF-8\r\n\r\n","mimeType":"text/html","requestHeaders":{"Host":"localhost:8889","Connection":"keep-alive","Upgrade-Insecure-Requests":"1","User-Agent":"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3494.0 Safari/537.36","Accept":"text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8","Accept-Encoding":"gzip, deflate, br","Accept-Language":"en-US,en;q=0.9","Cookie":"wordpress_23778236db82f19306f247e20a353a99=admin%7C1558202553%7CVuVC3Z18s9haDWOEEiOcN7Z4NWd3jdjorB94Vm6SErb%7C10b74bec70ab51a52c5d7b6c5dd4ea17fb80e6299d88b979e47b996c7fd24d3c; wordpress_test_cookie=WP+Cookie+check; wordpress_logged_in_23778236db82f19306f247e20a353a99=admin%7C1558202553%7CVuVC3Z18s9haDWOEEiOcN7Z4NWd3jdjorB94Vm6SErb%7C66d3f40ceebce50047aad36163b9a95b8348188efe559cb40f6971279586fa1e; wp-settings-1=editor%3Dtinymce; wp-settings-time-1=1558029753"},"requestHeadersText":"GET /wp-admin/post-new.php HTTP/1.1\r\nHost: localhost:8889\r\nConnection: keep-alive\r\nUpgrade-Insecure-Requests: 1\r\nUser-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3494.0 Safari/537.36\r\nAccept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8\r\nAccept-Encoding: gzip, deflate, br\r\nAccept-Language: en-US,en;q=0.9\r\nCookie: wordpress_23778236db82f19306f247e20a353a99=admin%7C1558202553%7CVuVC3Z18s9haDWOEEiOcN7Z4NWd3jdjorB94Vm6SErb%7C10b74bec70ab51a52c5d7b6c5dd4ea17fb80e6299d88b979e47b996c7fd24d3c; wordpress_test_cookie=WP+Cookie+check; wordpress_logged_in_23778236db82f19306f247e20a353a99=admin%7C1558202553%7CVuVC3Z18s9haDWOEEiOcN7Z4NWd3jdjorB94Vm6SErb%7C66d3f40ceebce50047aad36163b9a95b8348188efe559cb40f6971279586fa1e; wp-settings-1=editor%3Dtinymce; wp-settings-time-1=1558029753\r\n","connectionReused":true,"connectionId":192,"remoteIPAddress":"[::1]","remotePort":8889,"fromDiskCache":false,"fromServiceWorker":false,"encodedDataLength":0,"timing":{"requestTime":68261.694328,"proxyStart":-1,"proxyEnd":-1,"dnsStart":-1,"dnsEnd":-1,"connectStart":-1,"connectEnd":-1,"sslStart":-1,"sslEnd":-1,"workerStart":-1,"workerReady":-1,"sendStart":2.694,"sendEnd":2.737,"pushStart":0,"pushEnd":0,"receiveHeadersEnd":107.836},"protocol":"http/1.1","securityState":"neutral"},"frameId":"A966F77A1F3A97FF8CEEAD72EFE9B104"}}

The responseReceived event is only used to emit the Request "response" event. This event is not directly used by Gutenberg. It is used by waitForNavigation to get the response content, but it doesn't block the method.

Nothing in the Gutenberg e2e tests is making use of this event. It's only received because Puppeteer enabled the Network domain by default. As such it's not blocking out alpha release.

Depends on D74578

https://hg.mozilla.org/mozilla-central/rev/2518e3505983