A request from battre:


1) My first request would be an easier way to use chrome://ukm for checking whether the the UKM recording for your feature works.

Today, chrome://ukm is cumulative, this means:
- You open chrome://ukm
- You perform an action on a site to see whether the correct metrics are reported. 
- Unfortunately, you basically have to restart the browser if a) you made a mistake or b) you want to test the same behavior on a different domain, because by the time you perform the actions again, chrome://ukm will have accumulated so much data that it is really hard to stay on top of what has been reported for which site.

Related to this, it would be awesome to filter the types of metrics that are shown in chrome://ukm.

Part of what we can do for this work is to migrate it to webUI message handler. We did this for chrome://histograms, see:
https://chromium-review.googlesource.com/c/chromium/src/+/890627
https://chromium-review.googlesource.com/c/chromium/src/+/1065462

Hopefully looking at what was done for chrome://histograms will help.

We probably want to do this migration before more work.

After that I think we should try to add filtering.

Assigned to etienne for rotation project.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e67ba729fb0235a99f398b4f747681ee33be6783

commit e67ba729fb0235a99f398b4f747681ee33be6783
Author: Etienne Pierre-doray <etiennep@chromium.org>
Date: Fri Jul 20 22:49:34 2018

[Ukm] Implement ukm debug page with WebUI.

This CL refactors ukm debug page.
The new version uses WebUI and is implemented in
HTML/JS.

Bug:  843181 
Cq-Include-Trybots: luci.chromium.try:closure_compilation;luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I593518d10df17bb3c49961cb2ab590788b4d8efc
Reviewed-on: https://chromium-review.googlesource.com/1142481
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Reviewed-by: Peter Lee <pkl@chromium.org>
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577020}
[modify] https://crrev.com/e67ba729fb0235a99f398b4f747681ee33be6783/chrome/browser/BUILD.gn
[modify] https://crrev.com/e67ba729fb0235a99f398b4f747681ee33be6783/chrome/browser/browser_resources.grd
[modify] https://crrev.com/e67ba729fb0235a99f398b4f747681ee33be6783/chrome/browser/metrics/chrome_metrics_service_client.cc
[add] https://crrev.com/e67ba729fb0235a99f398b4f747681ee33be6783/chrome/browser/resources/ukm/BUILD.gn
[add] https://crrev.com/e67ba729fb0235a99f398b4f747681ee33be6783/chrome/browser/resources/ukm/ukm_internals.html
[add] https://crrev.com/e67ba729fb0235a99f398b4f747681ee33be6783/chrome/browser/resources/ukm/ukm_internals.js
[modify] https://crrev.com/e67ba729fb0235a99f398b4f747681ee33be6783/chrome/browser/ui/BUILD.gn
[modify] https://crrev.com/e67ba729fb0235a99f398b4f747681ee33be6783/chrome/browser/ui/webui/chrome_web_ui_controller_factory.cc
[add] https://crrev.com/e67ba729fb0235a99f398b4f747681ee33be6783/chrome/browser/ui/webui/ukm/ukm_internals_ui.cc
[add] https://crrev.com/e67ba729fb0235a99f398b4f747681ee33be6783/chrome/browser/ui/webui/ukm/ukm_internals_ui.h
[modify] https://crrev.com/e67ba729fb0235a99f398b4f747681ee33be6783/chrome/common/webui_url_constants.cc
[modify] https://crrev.com/e67ba729fb0235a99f398b4f747681ee33be6783/chrome/common/webui_url_constants.h
[delete] https://crrev.com/c64725f4494d84d223fa206f3059aa1d872253ea/components/ukm/content/debug_page/BUILD.gn
[delete] https://crrev.com/c64725f4494d84d223fa206f3059aa1d872253ea/components/ukm/content/debug_page/debug_page.cc
[delete] https://crrev.com/c64725f4494d84d223fa206f3059aa1d872253ea/components/ukm/content/debug_page/debug_page.h
[modify] https://crrev.com/e67ba729fb0235a99f398b4f747681ee33be6783/components/ukm/debug/ukm_debug_data_extractor.cc
[modify] https://crrev.com/e67ba729fb0235a99f398b4f747681ee33be6783/components/ukm/debug/ukm_debug_data_extractor.h
[modify] https://crrev.com/e67ba729fb0235a99f398b4f747681ee33be6783/ios/chrome/browser/ui/webui/url_keyed_metrics_ui.cc

My rotation is over. Transferring back to rkaplow.

iOS should be a quick fix. Working on that..

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/26fefaa121b7b0e86b139587cac2ffc22702dd2e

commit 26fefaa121b7b0e86b139587cac2ffc22702dd2e
Author: Moe Ahmadi <mahmadi@chromium.org>
Date: Tue Jul 24 16:14:49 2018

[IOS][UKM] Modifies UKM internals page (chrome://ukm) to use WebUI.

- Modifies iOS implementation of chrome://ukm to use WebUI.
- Refactors HTML/JS resources to be used in iOS.
- Removes method in ukm::UkmDebugDataExtractor that returns HTML debug data.
- Adds helper methods to resolve/reject Promises to WebUIIOS.

Bug:  843181 
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I008ce1beb8d35dd9d4a7fc482990f06e3095f16a
Reviewed-on: https://chromium-review.googlesource.com/1147241
Commit-Queue: Moe Ahmadi <mahmadi@chromium.org>
Reviewed-by: Peter Lee <pkl@chromium.org>
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577569}
[modify] https://crrev.com/26fefaa121b7b0e86b139587cac2ffc22702dd2e/chrome/browser/browser_resources.grd
[delete] https://crrev.com/0be56f3a61ac5bf2010458b6dd3a0ecce868b737/chrome/browser/resources/ukm/BUILD.gn
[delete] https://crrev.com/0be56f3a61ac5bf2010458b6dd3a0ecce868b737/chrome/browser/resources/ukm/ukm_internals.js
[modify] https://crrev.com/26fefaa121b7b0e86b139587cac2ffc22702dd2e/chrome/browser/ui/webui/ukm/ukm_internals_ui.cc
[modify] https://crrev.com/26fefaa121b7b0e86b139587cac2ffc22702dd2e/components/ukm/debug/BUILD.gn
[modify] https://crrev.com/26fefaa121b7b0e86b139587cac2ffc22702dd2e/components/ukm/debug/ukm_debug_data_extractor.cc
[modify] https://crrev.com/26fefaa121b7b0e86b139587cac2ffc22702dd2e/components/ukm/debug/ukm_debug_data_extractor.h
[rename] https://crrev.com/26fefaa121b7b0e86b139587cac2ffc22702dd2e/components/ukm/debug/ukm_internals.html
[add] https://crrev.com/26fefaa121b7b0e86b139587cac2ffc22702dd2e/components/ukm/debug/ukm_internals.js
[modify] https://crrev.com/26fefaa121b7b0e86b139587cac2ffc22702dd2e/ios/chrome/app/resources/ios_resources.grd
[modify] https://crrev.com/26fefaa121b7b0e86b139587cac2ffc22702dd2e/ios/chrome/browser/ui/webui/BUILD.gn
[modify] https://crrev.com/26fefaa121b7b0e86b139587cac2ffc22702dd2e/ios/chrome/browser/ui/webui/chrome_web_ui_ios_controller_factory.mm
[add] https://crrev.com/26fefaa121b7b0e86b139587cac2ffc22702dd2e/ios/chrome/browser/ui/webui/ukm_internals_ui.cc
[add] https://crrev.com/26fefaa121b7b0e86b139587cac2ffc22702dd2e/ios/chrome/browser/ui/webui/ukm_internals_ui.h
[delete] https://crrev.com/0be56f3a61ac5bf2010458b6dd3a0ecce868b737/ios/chrome/browser/ui/webui/url_keyed_metrics_ui.cc
[delete] https://crrev.com/0be56f3a61ac5bf2010458b6dd3a0ecce868b737/ios/chrome/browser/ui/webui/url_keyed_metrics_ui.h
[modify] https://crrev.com/26fefaa121b7b0e86b139587cac2ffc22702dd2e/ios/web/public/webui/web_ui_ios.h
[modify] https://crrev.com/26fefaa121b7b0e86b139587cac2ffc22702dd2e/ios/web/webui/web_ui_ios_impl.h
[modify] https://crrev.com/26fefaa121b7b0e86b139587cac2ffc22702dd2e/ios/web/webui/web_ui_ios_impl.mm

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a175853cc521f754e17d1e69bf23f63736a929f0

commit a175853cc521f754e17d1e69bf23f63736a929f0
Author: Nikunj Bhagat <nikunjb@chromium.org>
Date: Fri Nov 09 00:36:18 2018

Add chrome://ukm debug ui

BUG= 843181 

Change-Id: I8b43a72535dd09a175df731a94dc8e216374e7ff
Reviewed-on: https://chromium-review.googlesource.com/c/1306660
Commit-Queue: Nik Bhagat <nikunjb@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: calamity <calamity@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606660}
[modify] https://crrev.com/a175853cc521f754e17d1e69bf23f63736a929f0/BUILD.gn
[modify] https://crrev.com/a175853cc521f754e17d1e69bf23f63736a929f0/chrome/android/javatests/src/org/chromium/chrome/browser/sync/UkmTest.java
[modify] https://crrev.com/a175853cc521f754e17d1e69bf23f63736a929f0/chrome/browser/browser_resources.grd
[modify] https://crrev.com/a175853cc521f754e17d1e69bf23f63736a929f0/chrome/browser/ui/webui/ukm/ukm_internals_ui.cc
[add] https://crrev.com/a175853cc521f754e17d1e69bf23f63736a929f0/components/ukm/debug/.eslintrc.js
[add] https://crrev.com/a175853cc521f754e17d1e69bf23f63736a929f0/components/ukm/debug/PRESUBMIT.py
[modify] https://crrev.com/a175853cc521f754e17d1e69bf23f63736a929f0/components/ukm/debug/ukm_debug_data_extractor.cc
[modify] https://crrev.com/a175853cc521f754e17d1e69bf23f63736a929f0/components/ukm/debug/ukm_debug_data_extractor.h
[add] https://crrev.com/a175853cc521f754e17d1e69bf23f63736a929f0/components/ukm/debug/ukm_internals.css
[modify] https://crrev.com/a175853cc521f754e17d1e69bf23f63736a929f0/components/ukm/debug/ukm_internals.html
[modify] https://crrev.com/a175853cc521f754e17d1e69bf23f63736a929f0/components/ukm/debug/ukm_internals.js

The new chrome://ukm UI should be easier to use. Please provide feedback or open separate bugs if something is not working as expected.