I think this should have the same priority as issue 678288, since 80+% of experiments are using this configuration on chrome. Probably the ratio might be lower on webview assuming that user visible experiments are more likely to use persistent consistency and webview may not have a lot of them, but it is still a high priority.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ef70c85e24ab28f8cc8d67666e6ee42ea62d4ab0

commit ef70c85e24ab28f8cc8d67666e6ee42ea62d4ab0
Author: Paul Miller <paulmiller@google.com>
Date: Wed Jul 25 21:31:31 2018

WebView: Ignore permanent-consistency experiments

Android WebView currently treats permanent-consistency experiments
(which are intended to retain their group assignments across runs) as
session-consistency (which are intended to be randomly assigned on each
run). It's safer to not apply permanent-consistency experiments to
WebView at all, to avoid mistakes.

BUG=866722

Change-Id: I9d501437718d934c2a59b95335c787302ce758e7
Reviewed-on: https://chromium-review.googlesource.com/1148991
Reviewed-by: Changwan Ryu <changwan@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Paul Miller <paulmiller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578070}
[modify] https://crrev.com/ef70c85e24ab28f8cc8d67666e6ee42ea62d4ab0/android_webview/browser/aw_variations_service_client.cc
[modify] https://crrev.com/ef70c85e24ab28f8cc8d67666e6ee42ea62d4ab0/android_webview/browser/aw_variations_service_client.h
[modify] https://crrev.com/ef70c85e24ab28f8cc8d67666e6ee42ea62d4ab0/components/variations/client_filterable_state.h
[modify] https://crrev.com/ef70c85e24ab28f8cc8d67666e6ee42ea62d4ab0/components/variations/service/BUILD.gn
[modify] https://crrev.com/ef70c85e24ab28f8cc8d67666e6ee42ea62d4ab0/components/variations/service/variations_field_trial_creator.cc
[add] https://crrev.com/ef70c85e24ab28f8cc8d67666e6ee42ea62d4ab0/components/variations/service/variations_service_client.cc
[modify] https://crrev.com/ef70c85e24ab28f8cc8d67666e6ee42ea62d4ab0/components/variations/service/variations_service_client.h
[modify] https://crrev.com/ef70c85e24ab28f8cc8d67666e6ee42ea62d4ab0/components/variations/study_filtering.cc

Please add the manual verification if required.

I don't think there's anything to verify yet. The above change is explicitly disables, rather than enables, this feature.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c2e430c4a5ef55038aac8df4f3e4537c55e65f0a

commit c2e430c4a5ef55038aac8df4f3e4537c55e65f0a
Author: Paul Miller <paulmiller@google.com>
Date: Tue Aug 28 18:52:34 2018

Enable persistent prefs in WebView

Google-internal design doc:
https://docs.google.com/document/d/1X6Xoz9hl3qoAj3EhAKcvZ6hWLVcY_QpQgmUexpgDHKA/edit?usp=sharing

Keep prefs that should be persisted across runs in a JsonPrefStore, and
other prefs in an InMemoryPrefStore. Use SegregatedPrefStore to dispatch
individual prefs to one or the other, based on a whitelist of persisted
prefs. The whitelist is currently empty; prefs will be added as features
require them.

Also keep pref_registry in a scoped_refptr, rather than a raw pointer,
for safety.

BUG=866722

Change-Id: I55c819b14f130849b2066321fa4042bb0bd2b5ea
Reviewed-on: https://chromium-review.googlesource.com/1189043
Reviewed-by: Richard Coles <torne@chromium.org>
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Commit-Queue: Paul Miller <paulmiller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#586801}
[modify] https://crrev.com/c2e430c4a5ef55038aac8df4f3e4537c55e65f0a/android_webview/BUILD.gn
[modify] https://crrev.com/c2e430c4a5ef55038aac8df4f3e4537c55e65f0a/android_webview/DEPS
[modify] https://crrev.com/c2e430c4a5ef55038aac8df4f3e4537c55e65f0a/android_webview/browser/aw_browser_context.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a0e799c6ffaf46f8e72b4aad8b13281a3de25671

commit a0e799c6ffaf46f8e72b4aad8b13281a3de25671
Author: Paul Miller <paulmiller@google.com>
Date: Fri Sep 07 21:23:34 2018

Create WebView's prefs earlier and use them for variations

Google-internal design doc:
https://docs.google.com/document/d/1X6Xoz9hl3qoAj3EhAKcvZ6hWLVcY_QpQgmUexpgDHKA/edit?usp=sharing

Move prefs creation from AwBrowserContext in PreMainMessageLoopRun to
AwBrowserMainParts in PreCreateThreads. This way, variations can use the
same pref service as the rest of WebView, while still being initialized
as early as possible. (See BrowserMainLoop::CreateStartupTasks() for an
overview of the startup sequence.)

Before, AwBrowserContext created and owned PrefService and
BrowserPolicyConnector. Now, AwBrowserMainParts creates them in
PreCreateThreads, and owns them until PreMainMessageLoopRun, at which
point ownership is transferred to AwBrowserContext.

BUG=866722

Change-Id: Ie8eb6df60bd4a0f872d8c6401cc14ff0bca38368
Reviewed-on: https://chromium-review.googlesource.com/1212268
Reviewed-by: Richard Coles <torne@chromium.org>
Commit-Queue: Paul Miller <paulmiller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589665}
[modify] https://crrev.com/a0e799c6ffaf46f8e72b4aad8b13281a3de25671/android_webview/BUILD.gn
[modify] https://crrev.com/a0e799c6ffaf46f8e72b4aad8b13281a3de25671/android_webview/browser/aw_browser_context.cc
[modify] https://crrev.com/a0e799c6ffaf46f8e72b4aad8b13281a3de25671/android_webview/browser/aw_browser_context.h
[modify] https://crrev.com/a0e799c6ffaf46f8e72b4aad8b13281a3de25671/android_webview/browser/aw_browser_main_parts.cc
[modify] https://crrev.com/a0e799c6ffaf46f8e72b4aad8b13281a3de25671/android_webview/browser/aw_browser_main_parts.h
[modify] https://crrev.com/a0e799c6ffaf46f8e72b4aad8b13281a3de25671/android_webview/browser/aw_content_browser_client.cc
[modify] https://crrev.com/a0e799c6ffaf46f8e72b4aad8b13281a3de25671/android_webview/browser/aw_content_browser_client.h
[modify] https://crrev.com/a0e799c6ffaf46f8e72b4aad8b13281a3de25671/android_webview/browser/aw_field_trial_creator.cc
[modify] https://crrev.com/a0e799c6ffaf46f8e72b4aad8b13281a3de25671/android_webview/browser/aw_field_trial_creator.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6bd4db44ab539859b70c348782ef3b0922ae2656

commit 6bd4db44ab539859b70c348782ef3b0922ae2656
Author: Paul Miller <paulmiller@google.com>
Date: Thu Sep 20 19:34:54 2018

WebView: Configure entropy providers

This is in preparation to enable permanent-consistency and GWS-visible
variations experiments in WebView.

For experiments which must keep the same group across runs, there are
"entropy providers" used to generate deterministic, pseudorandom group
assignments. Chrome has 2 providers: the "low entropy provider" is
seeded by kMetricsLowEntropySource; the "default entropy provider",
seeded by both the low entropy source, and also the UMA client ID, if
it's available. (If UMA is disabled, Chrome will have no client ID.)

WebView uses GMS to determine whether UMA is enabled, which is very
slow. So only use the low entropy provider in WebView, and seed it with
the low entropy source. (Before this change, WebView's provider was
seeded with the client ID, which has too many random bits, and blocked
enabling GWS-visible experiments.)

Since WebView no longer uses the client ID as an entropy source, we
don't need to load the ID so early in startup, so remove the code for
pre-loading the ID. It will only be loaded later, asynchronously, in
AwMetricsServiceClient.

AwFieldTrialCreator must call into MetricsStateManager to get these
entropy providers. But WebView's MetricsStateManager is owned by
AwMetricsServiceClient, which was not initialized until after
AwFieldTrialCreator. So initialize AwMetricsServiceClient sooner, and
within AwMetricsServiceClient, create the MetricsStateManager before the
asynchronous call, so that AwFieldTrialCreator can use it immediately.

AwFieldTrialCreator is now initialized with a null
URLRequestContextGetter. This is fine because this field is unused since
commit a5febff94dd70a488bd1. It will be removed in a separate change.

BUG=866722

Change-Id: I31451924e97406db8a9f3efadcab6402a07007ea
Reviewed-on: https://chromium-review.googlesource.com/1227531
Commit-Queue: Paul Miller <paulmiller@chromium.org>
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Bo <boliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592902}
[modify] https://crrev.com/6bd4db44ab539859b70c348782ef3b0922ae2656/android_webview/browser/aw_browser_context.cc
[modify] https://crrev.com/6bd4db44ab539859b70c348782ef3b0922ae2656/android_webview/browser/aw_browser_main_parts.cc
[modify] https://crrev.com/6bd4db44ab539859b70c348782ef3b0922ae2656/android_webview/browser/aw_field_trial_creator.cc
[modify] https://crrev.com/6bd4db44ab539859b70c348782ef3b0922ae2656/android_webview/browser/aw_metrics_service_client.cc
[modify] https://crrev.com/6bd4db44ab539859b70c348782ef3b0922ae2656/android_webview/browser/aw_metrics_service_client.h
[modify] https://crrev.com/6bd4db44ab539859b70c348782ef3b0922ae2656/android_webview/java/src/org/chromium/android_webview/AwMetricsServiceClient.java
[modify] https://crrev.com/6bd4db44ab539859b70c348782ef3b0922ae2656/android_webview/java/src/org/chromium/android_webview/VariationsSeedLoader.java

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5bc7e0faee56286f64f9dd3f86f4e819a2557507

commit 5bc7e0faee56286f64f9dd3f86f4e819a2557507
Author: Paul Miller <paulmiller@google.com>
Date: Fri Sep 21 17:07:42 2018

WebView: Only create one low entropy provider

Multiple CachingPermutedEntropyProvider objects would all try to cache
their values in the same pref store, overwriting each other's.

BUG=866722

Change-Id: I42efd8b4eaf5f0dfec9e2b1be1fcac51e2b481ab
Reviewed-on: https://chromium-review.googlesource.com/1236290
Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Reviewed-by: Bo <boliu@chromium.org>
Commit-Queue: Paul Miller <paulmiller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593238}
[modify] https://crrev.com/5bc7e0faee56286f64f9dd3f86f4e819a2557507/android_webview/browser/aw_field_trial_creator.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5d2f2dc7550c03eef7f506a79df939d75322c145

commit 5d2f2dc7550c03eef7f506a79df939d75322c145
Author: Paul Miller <paulmiller@google.com>
Date: Sat Sep 22 00:56:34 2018

WebView: Remove DoSetUpFieldTrials

Fold AwFieldTrialCreator::DoSetUpFieldTrials into
AwFieldTrialCreator::SetUpFieldTrials. The former is unnecessary since
AwFieldTrialCreator no longer requires the client ID, so
DoSetUpFieldTrials can no longer return early.

BUG=866722

Change-Id: Ibcce988656cabe57ed142abb14efbb163e0b3fb6
Reviewed-on: https://chromium-review.googlesource.com/1238485
Reviewed-by: Bo <boliu@chromium.org>
Commit-Queue: Paul Miller <paulmiller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593397}
[modify] https://crrev.com/5d2f2dc7550c03eef7f506a79df939d75322c145/android_webview/browser/aw_field_trial_creator.cc
[modify] https://crrev.com/5d2f2dc7550c03eef7f506a79df939d75322c145/android_webview/browser/aw_field_trial_creator.h

Please add the amnual verification steps if applicable. Thanks

This is not fixed, so can't be verified.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8bf4bf245ce923a47a49d6448a1ff20cf94e6ead

commit 8bf4bf245ce923a47a49d6448a1ff20cf94e6ead
Author: Paul Miller <paulmiller@chromium.org>
Date: Wed Sep 26 22:07:19 2018

Revert "WebView: Ignore permanent-consistency experiments"

This reverts commit ef70c85e24ab28f8cc8d67666e6ee42ea62d4ab0.

Reason for revert: WebView now supports permanent-consistency.

BUG=866722

Original change's description:
> WebView: Ignore permanent-consistency experiments
> 
> Android WebView currently treats permanent-consistency experiments
> (which are intended to retain their group assignments across runs) as
> session-consistency (which are intended to be randomly assigned on each
> run). It's safer to not apply permanent-consistency experiments to
> WebView at all, to avoid mistakes.
> 
> BUG=866722
> 
> Change-Id: I9d501437718d934c2a59b95335c787302ce758e7
> Reviewed-on: https://chromium-review.googlesource.com/1148991
> Reviewed-by: Changwan Ryu <changwan@chromium.org>
> Reviewed-by: Steven Holte <holte@chromium.org>
> Commit-Queue: Paul Miller <paulmiller@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#578070}

TBR=changwan@chromium.org,holte@chromium.org,paulmiller@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 866722
Change-Id: Ifd00450fbba1afc1db619109cf918ef75cbcf84f
Reviewed-on: https://chromium-review.googlesource.com/1237244
Reviewed-by: Paul Miller <paulmiller@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Paul Miller <paulmiller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594491}
[modify] https://crrev.com/8bf4bf245ce923a47a49d6448a1ff20cf94e6ead/android_webview/browser/aw_variations_service_client.cc
[modify] https://crrev.com/8bf4bf245ce923a47a49d6448a1ff20cf94e6ead/android_webview/browser/aw_variations_service_client.h
[modify] https://crrev.com/8bf4bf245ce923a47a49d6448a1ff20cf94e6ead/components/variations/client_filterable_state.h
[modify] https://crrev.com/8bf4bf245ce923a47a49d6448a1ff20cf94e6ead/components/variations/service/BUILD.gn
[modify] https://crrev.com/8bf4bf245ce923a47a49d6448a1ff20cf94e6ead/components/variations/service/variations_field_trial_creator.cc
[delete] https://crrev.com/dfdb89973b837679891ae2117dbea0060203bca7/components/variations/service/variations_service_client.cc
[modify] https://crrev.com/8bf4bf245ce923a47a49d6448a1ff20cf94e6ead/components/variations/service/variations_service_client.h
[modify] https://crrev.com/8bf4bf245ce923a47a49d6448a1ff20cf94e6ead/components/variations/study_filtering.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/bbac4d2c4c896f3bd836f825619c29ff219e9254

commit bbac4d2c4c896f3bd836f825619c29ff219e9254
Author: Paul Miller <paulmiller@chromium.org>
Date: Wed Oct 03 21:39:33 2018

Reland "WebView: Ignore permanent-consistency experiments"

This reverts commit 8bf4bf245ce923a47a49d6448a1ff20cf94e6ead.

Reason for revert: PermutedEntropyProvider regressed perf & memory.

BUG=890413

Original change's description:
> Revert "WebView: Ignore permanent-consistency experiments"
> 
> This reverts commit ef70c85e24ab28f8cc8d67666e6ee42ea62d4ab0.
> 
> Reason for revert: WebView now supports permanent-consistency.
> 
> BUG=866722
> 
> Original change's description:
> > WebView: Ignore permanent-consistency experiments
> > 
> > Android WebView currently treats permanent-consistency experiments
> > (which are intended to retain their group assignments across runs) as
> > session-consistency (which are intended to be randomly assigned on each
> > run). It's safer to not apply permanent-consistency experiments to
> > WebView at all, to avoid mistakes.
> > 
> > BUG=866722
> > 
> > Change-Id: I9d501437718d934c2a59b95335c787302ce758e7
> > Reviewed-on: https://chromium-review.googlesource.com/1148991
> > Reviewed-by: Changwan Ryu <changwan@chromium.org>
> > Reviewed-by: Steven Holte <holte@chromium.org>
> > Commit-Queue: Paul Miller <paulmiller@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#578070}
> 
> TBR=changwan@chromium.org,holte@chromium.org,paulmiller@chromium.org
> 
> # Not skipping CQ checks because original CL landed > 1 day ago.
> 
> Bug: 866722
> Change-Id: Ifd00450fbba1afc1db619109cf918ef75cbcf84f
> Reviewed-on: https://chromium-review.googlesource.com/1237244
> Reviewed-by: Paul Miller <paulmiller@chromium.org>
> Reviewed-by: Steven Holte <holte@chromium.org>
> Commit-Queue: Paul Miller <paulmiller@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#594491}

TBR=changwan@chromium.org,holte@chromium.org,paulmiller@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 866722
Change-Id: I58435ac0c107214e15b0e54ff8aee422eb98fa06
Reviewed-on: https://chromium-review.googlesource.com/c/1259807
Reviewed-by: Paul Miller <paulmiller@chromium.org>
Commit-Queue: Paul Miller <paulmiller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#596380}
[modify] https://crrev.com/bbac4d2c4c896f3bd836f825619c29ff219e9254/android_webview/browser/aw_variations_service_client.cc
[modify] https://crrev.com/bbac4d2c4c896f3bd836f825619c29ff219e9254/android_webview/browser/aw_variations_service_client.h
[modify] https://crrev.com/bbac4d2c4c896f3bd836f825619c29ff219e9254/components/variations/client_filterable_state.h
[modify] https://crrev.com/bbac4d2c4c896f3bd836f825619c29ff219e9254/components/variations/service/BUILD.gn
[modify] https://crrev.com/bbac4d2c4c896f3bd836f825619c29ff219e9254/components/variations/service/variations_field_trial_creator.cc
[add] https://crrev.com/bbac4d2c4c896f3bd836f825619c29ff219e9254/components/variations/service/variations_service_client.cc
[modify] https://crrev.com/bbac4d2c4c896f3bd836f825619c29ff219e9254/components/variations/service/variations_service_client.h
[modify] https://crrev.com/bbac4d2c4c896f3bd836f825619c29ff219e9254/components/variations/study_filtering.cc

francos66040@gmail.com

Paul, do we have any automated testing around this feature? If not, could you add  some?

Yes.

https://chromium-review.googlesource.com/c/chromium/src/+/1322350/7/components/variations/variations_murmur_hash_unittest.cc
https://chromium-review.googlesource.com/c/chromium/src/+/1364344/7/components/metrics/metrics_state_manager_unittest.cc

Thanks. Any chance that we can add automated testing around the permanent consistency as well? Would it be possible for the test runner to finish the instrumentation and start a new one in the middle of testing?

There were already various tests involving permanent consistency:
https://cs.chromium.org/search/?q=permanent+file:%5Esrc/components/variations/.*test

I don't think it's possible to test multiple WebView startups in the same test. We'll have to use manual testing for that.

Agreed. Thanks.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f4799c73dad96edcd2f141337dd885ef5506d749

commit f4799c73dad96edcd2f141337dd885ef5506d749
Author: Paul Miller <paulmiller@google.com>
Date: Fri Dec 21 01:06:44 2018

WebView: Enable permanent-consistency variations studies

This has the immediate effect of enabling the 6 UMA-Uniformity-Trial-*
studies, which don't control any features.

Tested correctness like so:
1) Install WebViewLogVerbosifier.apk to enable study logging.
2) Use --disable-field-trial-config to test with the studies from the
    Finch seed, as opposed to the built-in test studies.
3) Run an app that uses WebView (and possibly restart the app, deleting
    variations_stamp in between, until it actually gets the seed).
4) Check for "Active field trial $FOO in group $BAR" in logcat, and that
    these lines include any relevant permanent-consistency studies.
5) Restart the app.
6) Check logcat again and verify that any permanent-consistency studies
    got the same group assignments.
7) Add --reset-variation-state to clear the low-entropy source value.
8) Restart the app.
6) Check logcat again; any permanent-consistency studies may now have
    different groups.

Tested performance like so:
1) Build official, non-component Monochrome with/without this change.
2) Install on Marlin with latest Android.
3) $ third_party/android_tools/sdk/platform-tools/systrace/systrace.py \
      -o ~/trace.html -a org.chromium.webview_shell webview
4) Run SystemWebViewShell.apk several times and note
    WebViewChromiumAwInit.startChromiumLocked wall time.

...and found not much difference. startChromiumLocked takes ~95-105
milliseconds in either case.

NormalizedMurmurHashEntropyProvider::GetEntropyForTrial itself averages
32 microseconds per study on Marlin (measured with base::ElapsedTimer).

BUG=866722

Change-Id: I630f6886cbd0ba803d6a4aba6aaf1fafd07f1cd9
Reviewed-on: https://chromium-review.googlesource.com/c/1385849
Commit-Queue: Paul Miller <paulmiller@chromium.org>
Reviewed-by: Changwan Ryu <changwan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#618416}
[modify] https://crrev.com/f4799c73dad96edcd2f141337dd885ef5506d749/android_webview/browser/aw_variations_service_client.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b858a2423714eb0f8d9326f3c77af3b43850583c

commit b858a2423714eb0f8d9326f3c77af3b43850583c
Author: Paul Miller <paulmiller@google.com>
Date: Wed Jan 02 19:37:35 2019

WebView: Activate AndroidWebViewConsistencyTest

This study doesn't do anything except exercise permanent-consistency.
Query it once to "activate" it, so it shows up in the logs when
WebViewLogVerbosifier.apk is installed, so QA can verify
permanent-consistency.

BUG=866722

Change-Id: I2b2c6812b735a7bd0cee8c116161d2e18c5a27f3
Reviewed-on: https://chromium-review.googlesource.com/c/1389437
Reviewed-by: Changwan Ryu <changwan@chromium.org>
Commit-Queue: Paul Miller <paulmiller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619456}
[modify] https://crrev.com/b858a2423714eb0f8d9326f3c77af3b43850583c/android_webview/browser/aw_feature_list_creator.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/540ef48f7c2136829cfd43de2c774f3fadba5990

commit 540ef48f7c2136829cfd43de2c774f3fadba5990
Author: Alexei Svitkine <asvitkine@chromium.org>
Date: Thu Jan 03 19:00:56 2019

Reset old low entropy source when reseting all client ids.

This is triggered by the cloned install detector here:
https://cs.chromium.org/chromium/src/components/metrics/cloned_install_detector.cc?rcl=4c806b8b802c5bcd93831229bedd8164d8a68a26&l=82

Bug: 866722
Change-Id: Ic0c99bdceee10413949f71f965d1b4edb9006466
Reviewed-on: https://chromium-review.googlesource.com/c/1392348
Reviewed-by: Paul Miller <paulmiller@chromium.org>
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619705}
[modify] https://crrev.com/540ef48f7c2136829cfd43de2c774f3fadba5990/components/metrics/metrics_state_manager.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7ceb27aaaf6fe73e7902c88ce2bd032edc78ec49

commit 7ceb27aaaf6fe73e7902c88ce2bd032edc78ec49
Author: Paul Miller <paulmiller@google.com>
Date: Sun Jan 20 02:35:38 2019

WebView: Activate AndroidWebViewSessionConsistencyTest

This study doesn't do anything except exercise session-consistency.
Query it once to "activate" it, so it shows up in the logs when
WebViewLogVerbosifier.apk is installed, so QA can verify
permanent-consistency.

BUG=866722

Change-Id: I435b6ed5c93e105ebb49705078f4362eb46e109b
Reviewed-on: https://chromium-review.googlesource.com/c/1423837
Commit-Queue: Changwan Ryu <changwan@chromium.org>
Reviewed-by: Changwan Ryu <changwan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624482}
[modify] https://crrev.com/7ceb27aaaf6fe73e7902c88ce2bd032edc78ec49/android_webview/browser/aw_feature_list_creator.cc