It's really blocked on having some metrics, could be crbug.com/864625 or  crbug.com/905678 .

 crbug.com/905678  fits better. I have worked on it, hopefully it won't block you soon:)

https://chromium-review.googlesource.com/c/chromium/src/+/1355244/

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8dfddfccbd029409ac24992a76c6f926e5818934

commit 8dfddfccbd029409ac24992a76c6f926e5818934
Author: Henrique Nakashima <hnakashima@chromium.org>
Date: Thu Nov 29 21:44:07 2018

Check AllowStartingServiceManagerOnly in ServiceManagerStartupUtils.

AllowStartingServiceManagerOnly already gates starting the service
manager early in the native code. Make the Java code check the flag
too.

Bug:  899225 , 899226 
Change-Id: Iadc7d03b4e3b559815a72de66ff249f2ad36bbbb
Reviewed-on: https://chromium-review.googlesource.com/c/1318362
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Ken Rockot <rockot@google.com>
Reviewed-by: Xi Han <hanxi@chromium.org>
Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612380}
[modify] https://crrev.com/8dfddfccbd029409ac24992a76c6f926e5818934/chrome/android/java/src/org/chromium/chrome/browser/ChromeFeatureList.java
[modify] https://crrev.com/8dfddfccbd029409ac24992a76c6f926e5818934/chrome/android/java/src/org/chromium/chrome/browser/init/ServiceManagerStartupUtils.java
[modify] https://crrev.com/8dfddfccbd029409ac24992a76c6f926e5818934/chrome/browser/android/chrome_feature_list.cc
[modify] https://crrev.com/8dfddfccbd029409ac24992a76c6f926e5818934/content/app/content_main_runner_impl.cc
[modify] https://crrev.com/8dfddfccbd029409ac24992a76c6f926e5818934/content/public/common/content_features.cc
[modify] https://crrev.com/8dfddfccbd029409ac24992a76c6f926e5818934/content/public/common/content_features.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/fb181327ccbc75581d8ce46148c45ec7746f14a6

commit fb181327ccbc75581d8ce46148c45ec7746f14a6
Author: Xi Han <hanxi@google.com>
Date: Fri Nov 30 16:05:26 2018

Update commandline flags for ServicificationBackgroundServiceTest.

This is a follow for CL (https://crrev.com/c/1318362) which changes
"AllowStartingServiceManagerOnly" from commandline flag to a feature.
Update the ServicificationBackgroundServiceTest accordingly which has
this flag turned on.

Bug:  899225 
Change-Id: Ia1256af793cf6a49c7b6aaa88b4fa95bf619b657
Reviewed-on: https://chromium-review.googlesource.com/c/1357000
Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Commit-Queue: Xi Han <hanxi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612664}
[modify] https://crrev.com/fb181327ccbc75581d8ce46148c45ec7746f14a6/chrome/android/javatests/src/org/chromium/chrome/browser/ServicificationBackgroundServiceTest.java

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/52d7695149c1dcc26552fab8fc56cd83c225631b

commit 52d7695149c1dcc26552fab8fc56cd83c225631b
Author: Henrique Nakashima <hnakashima@chromium.org>
Date: Fri Nov 30 19:35:58 2018

Add AllowStartingServiceManagerOnly to about flags.

Bug:  899225 
Change-Id: I3b8a74fadcd4ae1821654e4c37bdbf7985787e72
Reviewed-on: https://chromium-review.googlesource.com/c/1340780
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Min Qin <qinmin@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612726}
[modify] https://crrev.com/52d7695149c1dcc26552fab8fc56cd83c225631b/chrome/browser/about_flags.cc
[modify] https://crrev.com/52d7695149c1dcc26552fab8fc56cd83c225631b/chrome/browser/flag-metadata.json
[modify] https://crrev.com/52d7695149c1dcc26552fab8fc56cd83c225631b/chrome/browser/flag_descriptions.cc
[modify] https://crrev.com/52d7695149c1dcc26552fab8fc56cd83c225631b/chrome/browser/flag_descriptions.h
[modify] https://crrev.com/52d7695149c1dcc26552fab8fc56cd83c225631b/tools/metrics/histograms/enums.xml