I will take a look into that.

Question - should the enable_brotli be set true only in the main URLRequestContext object - https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/net/chrome_url_request_context_getter.cc&l=54&gs=cpp:%253Canonymous-namespace%253E::class-FactoryForMain::Create()@chromium/../../chrome/browser/net/chrome_url_request_context_getter.cc%257Cdef&gsn=Create&ct=xref_usages ????

You could also set it on the SystemURLRequestContext - make the bool a member of IOThread::Globals, and set it on the SystemURLRequestContext, and the profile's main request context in ProfileIOData::Init.

Then make URLRequestContext::CopyFrom copy it, and it should propogate to the other URLRequestContext that piggy back off of the main one.  Don't think we need to worry about anything else.

https://codereview.chromium.org/1919673003/

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3d40c8112303a985fab79c74e92e9a79fc4ac9f9

commit 3d40c8112303a985fab79c74e92e9a79fc4ac9f9
Author: maksim.sisov <maksim.sisov@intel.com>
Date: Mon May 02 13:27:16 2016

Move bool enable_brotli from HttpNetworkSession::Params

Moving bool enable_brotli from HttpNetoworkSession::Params
to URLRequestContext.

Brotli is set on thread initialization and profileiodata initialization.
Then it is propagated to other contexts through
URLRequestContext::CopyFrom method.

BUG= 600450 

Review-Url: https://codereview.chromium.org/1922403002
Cr-Commit-Position: refs/heads/master@{#390930}

[modify] https://crrev.com/3d40c8112303a985fab79c74e92e9a79fc4ac9f9/chrome/browser/io_thread.cc
[modify] https://crrev.com/3d40c8112303a985fab79c74e92e9a79fc4ac9f9/chrome/browser/io_thread.h
[modify] https://crrev.com/3d40c8112303a985fab79c74e92e9a79fc4ac9f9/chrome/browser/profiles/profile_io_data.cc
[modify] https://crrev.com/3d40c8112303a985fab79c74e92e9a79fc4ac9f9/net/http/http_network_session.cc
[modify] https://crrev.com/3d40c8112303a985fab79c74e92e9a79fc4ac9f9/net/http/http_network_session.h
[modify] https://crrev.com/3d40c8112303a985fab79c74e92e9a79fc4ac9f9/net/url_request/url_request_context.cc
[modify] https://crrev.com/3d40c8112303a985fab79c74e92e9a79fc4ac9f9/net/url_request/url_request_context.h
[modify] https://crrev.com/3d40c8112303a985fab79c74e92e9a79fc4ac9f9/net/url_request/url_request_http_job.cc
[modify] https://crrev.com/3d40c8112303a985fab79c74e92e9a79fc4ac9f9/net/url_request/url_request_http_job_unittest.cc