The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e387515081732b26380ee281e1a2ae94474becc2

commit e387515081732b26380ee281e1a2ae94474becc2
Author: Tarun Bansal <tbansal@chromium.org>
Date: Thu Mar 29 20:37:53 2018

Experiment with delaying requests fetched from spdy/h2/quic proxies

This experiment affects only http resources that
are fetched from a SPDY/H2/QUIC proxies.

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_mojo
Change-Id: Ifee25862f6720669536b0467c22218d0eb63b1f5
Bug:  826558 
Reviewed-on: https://chromium-review.googlesource.com/907669
Reviewed-by: Matt Menke <mmenke@chromium.org>
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#546934}
[modify] https://crrev.com/e387515081732b26380ee281e1a2ae94474becc2/services/network/resource_scheduler.cc
[modify] https://crrev.com/e387515081732b26380ee281e1a2ae94474becc2/services/network/resource_scheduler_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/15d588fff0ac8d3032aada1f55bd697b6a70246c

commit 15d588fff0ac8d3032aada1f55bd697b6a70246c
Author: Tarun Bansal <tbansal@chromium.org>
Date: Wed May 02 01:33:58 2018

Enable SpdyProxiesRequestsDelayable by default in developer builds

Change-Id: Ia4ad8b4647432352928e23e5cbc6e4c29cfa0443
Bug:  826558 
Reviewed-on: https://chromium-review.googlesource.com/1035444
Reviewed-by: Doug Arnett <dougarnett@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#555272}
[modify] https://crrev.com/15d588fff0ac8d3032aada1f55bd697b6a70246c/testing/variations/fieldtrial_testing_config.json

This is enabled for 100% population now.