I'm not familiar with the details of gerrit, but it seems that this simple deps.js file takes ages to download given its relatively small size of 1.9 KB.
It seems this file wouldn't change much, yet it's marked as no-cache if I'm not mistaken.
Though probably the deps.js file is not really an offender, it seems suspicious that most file requests happen right after this one finished (at around 750ms, see Screenshot)
RESPONSE HEADERS from DevTools:
alt-svc: hq=":443"; ma=2592000; quic=51303432; quic=51303431; quic=51303339; quic=51303335,quic=":443"; ma=2592000; v="42,41,39,35"
cache-control: no-cache, no-store, max-age=0, must-revalidate
content-security-policy-report-only: object-src 'none';script-src 'self' *.googlesource.com www.google-analytics.com apis.google.com www.google.com 'unsafe-inline' 'unsafe-eval';base-uri 'self' https://cdn.googlesource.com;report-uri https://csp-collector.appspot.com/csp/gerritcodereview/484.0
content-type: text/html; charset=utf-8
date: Wed, 11 Apr 2018 21:20:22 GMT
expires: Mon, 01 Jan 1990 00:00:00 GMT
set-cookie: XSRF_TOKEN=ANR1CjjU5qOhZrEjauAD7Q-VY_hW-iY_h1YmX4qqbbrlnSof0oH4lTlY_AMQAKYT9qpogi8t6jb54tm30R9Tf7wGZQjoGNcLwg; Path=/; Secure
strict-transport-security: max-age=31536000; includeSubDomains; preload
x-xss-protection: 1; mode=block