Once AccessTokenStore is eliminated, GeolocationDelegate will only be used to override the system provider. We need to keep this functionality, as it's used at least by Qt:

https://www.google.com/url?q=https://code.woboq.org/qt5/qtwebengine/src/core/content_browser_client_qt.cpp.html%23_ZN15QtWebEngineCore12_GLOBAL__N_121GeolocationDelegateQt30OverrideSystemLocationProviderEv&sa=D&ust=1506679470748000&usg=AFQjCNGRtz1iXhia6Iwx_L5Ak-01ouirOQ

Our plan for moving this functionality away from GeolocationDelegate is to inject it into the DeviceService constructor via ContentBrowserClient in a manner similar to the injection of the URLRequestContextGetter. Some initial thoughts from amoylan@:

base::Bind(&ContentBrowserClient::GetCustomSystemLocationProvider(), Unretained(GetContentClient()->browser()))

in to Geolocation, initially via a static setter.

The ContentBrowserClient::GetCustomSystemLocationProvider would want to proclaim itself to be callable from any thread to avoid introducing a new async stage in geolocation startup, which seems fine.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b67a7910293e914232d55cf76b4712b485f3bd69

commit b67a7910293e914232d55cf76b4712b485f3bd69
Author: Ke He <ke.he@intel.com>
Date: Mon Nov 27 23:25:55 2017

Eliminate GeolocationDelegate.

In this CL we remove the GeolocationDelegate but keep its functionality by
inject a GetCustomeSystemLocationProviderCallback to constructor of the Device
Service.

1) Add the GetCustomSystemLocationProvider() in ContentBrowserClient for
   embedder to override, and inject it to DeviceService constructor.
2) Move the location_provider.h to public/cpp.
3) Change the unittest of LocationArbitrator accordingly.

BUG= 725057 

Change-Id: I605d282cac2082f69526675a8e7dff3a46bafd74
Reviewed-on: https://chromium-review.googlesource.com/768614
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Tim Volodine <timvolodine@chromium.org>
Reviewed-by: Colin Blundell <blundell@chromium.org>
Commit-Queue: Ke He <ke.he@intel.com>
Cr-Commit-Position: refs/heads/master@{#519446}
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/content/browser/service_manager/service_manager_context.cc
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/content/public/browser/DEPS
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/content/public/browser/content_browser_client.cc
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/content/public/browser/content_browser_client.h
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/device/geolocation/BUILD.gn
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/device/geolocation/fake_location_provider.h
[delete] https://crrev.com/414a100e00163ba2ed3b66c0094ca52709ec3b24/device/geolocation/geolocation_delegate.cc
[delete] https://crrev.com/414a100e00163ba2ed3b66c0094ca52709ec3b24/device/geolocation/geolocation_delegate.h
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/device/geolocation/geolocation_provider.h
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/device/geolocation/geolocation_provider_impl.cc
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/device/geolocation/geolocation_provider_impl.h
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/device/geolocation/location_arbitrator.cc
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/device/geolocation/location_arbitrator.h
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/device/geolocation/location_arbitrator_unittest.cc
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/device/geolocation/location_provider_android.h
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/device/geolocation/network_location_provider.h
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/device/geolocation/public/cpp/BUILD.gn
[rename] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/device/geolocation/public/cpp/location_provider.h
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/services/device/BUILD.gn
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/services/device/device_service.cc
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/services/device/device_service.h
[modify] https://crrev.com/b67a7910293e914232d55cf76b4712b485f3bd69/services/device/device_service_test_base.cc