Please note that "metrics service" is already a thing (components/metrics/metrics_service.cc) so using that term to refer to the mojo service is confusing, because you're referring to something else than metrics_service.cc.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/fd9dcefaa399277d5d7236d22f02a03d9b0382a9

commit fd9dcefaa399277d5d7236d22f02a03d9b0382a9
Author: Mounir Lamouri <mlamouri@chromium.org>
Date: Thu Jul 06 10:26:55 2017

Move components/ukm/public/ to services/metrics/public/.

This will allow Blink to use the UKM service while it is transitionned
to be an actual service.

Bug:  733995 
Change-Id: I36aaace7daf159a03c2ccd401b39371ab3a26d82
Reviewed-on: https://chromium-review.googlesource.com/536933
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Colin Blundell <blundell@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#484530}
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/chrome/browser/DEPS
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/chrome/browser/android/contextualsearch/contextual_search_ranker_logger_impl.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/chrome/browser/android/contextualsearch/contextual_search_ranker_logger_impl.h
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/chrome/browser/metrics/ukm_browsertest.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/chrome/browser/page_load_metrics/observers/ukm_page_load_metrics_observer.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/chrome/browser/page_load_metrics/page_load_tracker.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/chrome/browser/password_manager/chrome_password_manager_client.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/chrome/browser/plugins/plugin_info_message_filter.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/chrome/browser/resource_coordinator/resource_coordinator_web_contents_observer.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/chrome/renderer/BUILD.gn
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/autofill/core/browser/DEPS
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/autofill/core/browser/autofill_metrics.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/autofill/core/browser/autofill_metrics.h
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/autofill/core/browser/form_structure.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/password_manager/core/browser/BUILD.gn
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/password_manager/core/browser/DEPS
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/password_manager/core/browser/password_form_metrics_recorder.h
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/password_manager/core/browser/password_form_metrics_recorder_unittest.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/password_manager/core/browser/password_manager_client.h
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/password_manager/core/browser/password_manager_metrics_recorder.h
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/password_manager/core/browser/password_manager_metrics_recorder_unittest.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/payments/core/DEPS
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/payments/core/journey_logger.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/translate/core/browser/DEPS
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/translate/core/browser/translate_ranker_impl.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/ukm/BUILD.gn
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/ukm/DEPS
[delete] https://crrev.com/18b1c7bb5c8ace4f38b7766727721e3f684bb0a5/components/ukm/public/ukm_export.h
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/ukm/ukm_interface.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/ukm/ukm_interface.h
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/ukm/ukm_recorder_impl.h
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/components/ukm/ukm_service_unittest.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/content/browser/BUILD.gn
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/content/browser/media/media_internals.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/content/browser/renderer_host/input/render_widget_host_latency_tracker.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/content/browser/renderer_host/input/render_widget_host_latency_tracker.h
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/content/browser/renderer_host/render_widget_host_delegate.h
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/content/browser/web_contents/web_contents_impl.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/content/browser/web_contents/web_contents_impl.h
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/content/renderer/BUILD.gn
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/content/renderer/DEPS
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[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/ios/chrome/browser/DEPS
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/ios/chrome/browser/application_context_impl.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/ios/chrome/browser/passwords/ios_chrome_password_manager_client.mm
[add] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/metrics/OWNERS
[add] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/metrics/README.md
[rename] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/metrics/public/cpp/BUILD.gn
[add] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/metrics/public/cpp/metrics_export.h
[rename] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/metrics/public/cpp/mojo_ukm_recorder.cc
[rename] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/metrics/public/cpp/mojo_ukm_recorder.h
[rename] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/metrics/public/cpp/ukm_entry_builder.cc
[rename] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/metrics/public/cpp/ukm_entry_builder.h
[rename] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/metrics/public/cpp/ukm_recorder.cc
[rename] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/metrics/public/cpp/ukm_recorder.h
[rename] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/metrics/public/interfaces/BUILD.gn
[rename] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/metrics/public/interfaces/OWNERS
[rename] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/metrics/public/interfaces/ukm_interface.mojom
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/resource_coordinator/DEPS
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/resource_coordinator/coordination_unit/coordination_unit_manager.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/resource_coordinator/public/interfaces/BUILD.gn
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/resource_coordinator/public/interfaces/service_callbacks.mojom
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/resource_coordinator/resource_coordinator_service.h
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/resource_coordinator/service_callbacks_impl.cc
[modify] https://crrev.com/fd9dcefaa399277d5d7236d22f02a03d9b0382a9/services/resource_coordinator/service_callbacks_impl.h

hey is there any outstanding work here or can we close?

The code moved to the services code but doesn't run as a service, does it?

I guess I misunderstood since I don't know much about serviceication - i thought having it be a mojo interface would be enough for other processes to be able to collect to UKM.

Would you mind giving a bit more information here on what this would allow us to do, or is this an improvement needed for all mojo interfaces?

My understanding is that, right now UKM's mojo interface is a capability off the browser process, rather than as a capability of a UKM service.

Moving forward, rather than UKM running as a service, it may make sense to just have it be a capability of a larger metrics service.  

Either way, the next step is probably to convert it to being a capability off of an metrics/ukm service embedded in the browser process.  I don't know that that makes it more broadly usable currently, but it would mean less change if metrics stopped being embedded in the browser and could run independently.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e830e7e38a287e5312e21db9f5aeb080d7bc30c8

commit e830e7e38a287e5312e21db9f5aeb080d7bc30c8
Author: Steven Holte <holte@google.com>
Date: Tue Nov 07 23:47:30 2017

Move url_keyed_metrics capability from browser to an embedded service.

This removes the need for resource_coordinator service to have
SetUkmRecorder interface, and just has it bind directly.

Also introduces MojoUkmRecorder::Create to access this service, and
uses this from Document::UkmRecorder().

Bug:  733995 

Change-Id: Ie8320cbd12c54af90e35ba21b8f30eb4e3ef4a0b
Reviewed-on: https://chromium-review.googlesource.com/611560
Commit-Queue: Steven Holte <holte@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: oysteine <oysteine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#514656}
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/chrome/app/BUILD.gn
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/chrome/browser/BUILD.gn
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/chrome/browser/DEPS
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[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/chrome/browser/chrome_content_browser_manifest_overlay.json
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/chrome/browser/resource_coordinator/resource_coordinator_web_contents_observer.cc
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/chrome/browser/resource_coordinator/resource_coordinator_web_contents_observer.h
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/components/ukm/BUILD.gn
[delete] https://crrev.com/d5cf29a85fff3fd471d9223fe05cd112c09debbb/components/ukm/ukm_interface.cc
[delete] https://crrev.com/d5cf29a85fff3fd471d9223fe05cd112c09debbb/components/ukm/ukm_interface.h
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/content/public/app/mojo/content_browser_manifest.json
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/content/public/app/mojo/content_renderer_manifest.json
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[add] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/services/metrics/manifest.json
[add] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/services/metrics/metrics_mojo_service.cc
[add] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/services/metrics/metrics_mojo_service.h
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/services/metrics/public/cpp/BUILD.gn
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/services/metrics/public/cpp/mojo_ukm_recorder.cc
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/services/metrics/public/cpp/mojo_ukm_recorder.h
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/services/metrics/public/cpp/ukm_recorder.h
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/services/metrics/public/interfaces/BUILD.gn
[add] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/services/metrics/public/interfaces/constants.mojom
[add] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/services/metrics/ukm_recorder_interface.cc
[add] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/services/metrics/ukm_recorder_interface.h
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/services/resource_coordinator/BUILD.gn
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/services/resource_coordinator/manifest.json
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/services/resource_coordinator/public/interfaces/BUILD.gn
[delete] https://crrev.com/d5cf29a85fff3fd471d9223fe05cd112c09debbb/services/resource_coordinator/public/interfaces/service_callbacks.mojom
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/services/resource_coordinator/resource_coordinator_service.cc
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/services/resource_coordinator/resource_coordinator_service.h
[delete] https://crrev.com/d5cf29a85fff3fd471d9223fe05cd112c09debbb/services/resource_coordinator/service_callbacks_impl.cc
[delete] https://crrev.com/d5cf29a85fff3fd471d9223fe05cd112c09debbb/services/resource_coordinator/service_callbacks_impl.h
[modify] https://crrev.com/e830e7e38a287e5312e21db9f5aeb080d7bc30c8/third_party/WebKit/Source/core/dom/Document.cpp