This is the top crash in latest canary-66.0.3355.0 with 60+ reprots/unique clients.

Link to the builds which introduced the crash:

https://crash.corp.google.com/browse?q=product.name%3D%27Chrome%27%20AND%20expanded_custom_data.ChromeCrashProto.ptype%3D%27browser%27%20AND%20expanded_custom_data.ChromeCrashProto.magic_signature_1.name%3D%27net%3A%3AURLRequestContext%3A%3AAssertNoURLRequests%27#productversion:1000,-magicsignature:50,-magicsignature2:50,-stablesignature:50,-magicsignaturesorted:50

Can we have a fix soon preferably before M66 hits beta.

Working on it...Have 8 code review requests pending, and having trouble getting a regression test working, though, so can make no promises.

Users experienced this crash on the following builds:

Win Canary 66.0.3355.0 -  1.19 CPM, 34 reports, 32 clients (signature net::URLRequestContext::AssertNoURLRequests)
Mac Canary 66.0.3355.0 -  2.01 CPM, 17 reports, 16 clients (signature net::URLRequestContext::AssertNoURLRequests)

If this update was incorrect, please add "Fracas-Wrong" label to prevent future updates.

- Go/Fracas

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d9ec7077b9e1094f6cee2ce7921386d1763bd6c4

commit d9ec7077b9e1094f6cee2ce7921386d1763bd6c4
Author: Matt Menke <mmenke@chromium.org>
Date: Wed Feb 28 01:13:36 2018

Fix AssertNoURLRequests crash in system request context.

This issue was caused by calling AssertNoURLRequests on the
SystemRequestContext before the NetworkContext (Which may own
URLLoaders) was torn down. Since the NetworkContext also owns the
SystemRequestContext, the solution was just to remove the
AssertNoURLRequests call.  URLRequestContextBuilder's URLRequestContext
implementation calls it, anyways.

This CL also moves NetworkQualityEstimator above the NetworkContext,
so it will be destroyed after the NetworkContext, which is needed if
there are live requests during NetworkContext teardown.

Bug:  816572 
Change-Id: Ief3ca156d8c5edc8205bba7aaa22a24ec4fdb066
Reviewed-on: https://chromium-review.googlesource.com/939742
Commit-Queue: Matt Menke <mmenke@chromium.org>
Reviewed-by: Randy Smith <rdsmith@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539609}
[modify] https://crrev.com/d9ec7077b9e1094f6cee2ce7921386d1763bd6c4/chrome/browser/io_thread.cc
[modify] https://crrev.com/d9ec7077b9e1094f6cee2ce7921386d1763bd6c4/chrome/browser/io_thread.h
[modify] https://crrev.com/d9ec7077b9e1094f6cee2ce7921386d1763bd6c4/chrome/browser/net/network_context_configuration_browsertest.cc
[modify] https://crrev.com/d9ec7077b9e1094f6cee2ce7921386d1763bd6c4/net/test/embedded_test_server/controllable_http_response.cc

Not seeing any on today's canary, so seems like that fixed it (or I've managed to change the stack trace, I suppose).