This is fixed now https://codereview.chromium.org/2501193003/

Yipeng's automated registration CL ran into some problems that means it doesn't look like the work here is complete:

1) There's still two callsites that use GetLibraryProcessType to determine what to call JNI registration for, instead of the selective registration, 
in chrome/app/android/chrome_jni_onload.cc and content/app/android/library_loader_hooks.cc

2) Monochrome still uses GetLibraryProcessType to decide which init function to call; this should be replaced with actual separate entry points.

3) GetLibraryProcessType never got removed from anywhere.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/894b62e67820e4a206b062ee39d13498cde3d6cd

commit 894b62e67820e4a206b062ee39d13498cde3d6cd
Author: Yipeng Wang <yipengw@chromium.org>
Date: Wed Jun 28 18:06:33 2017

Enable selective JNI registration for non-browser processes.

Currently we only enable the selective JNI registration for the renderer
process on the Java side, but use it to decide if a process is a browser
process or not on the native side.

Change: Enable the selective JNI registration for all non-browser processes
on Java side.

Bug: 674937
Change-Id: If97814bc5d79cfaa0211e46f785dbab329429d22
Reviewed-on: https://chromium-review.googlesource.com/552778
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
Commit-Queue: Yipeng Wang <yipengw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#483059}
[modify] https://crrev.com/894b62e67820e4a206b062ee39d13498cde3d6cd/content/public/android/java/src/org/chromium/content/app/ContentChildProcessServiceDelegate.java

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4fc72d112fd1b53bd7a0136f0204f182fe3c3310

commit 4fc72d112fd1b53bd7a0136f0204f182fe3c3310
Author: Yuly Novikov <ynovikov@chromium.org>
Date: Wed Jun 28 23:50:39 2017

Revert "Enable selective JNI registration for non-browser processes."

This reverts commit 894b62e67820e4a206b062ee39d13498cde3d6cd.

Reason for revert: crashes in https://build.chromium.org/p/chromium.gpu.fyi/builders/Android%20Release%20%28Nexus%205X%29/builds/8970

Original change's description:
> Enable selective JNI registration for non-browser processes.
> 
> Currently we only enable the selective JNI registration for the renderer
> process on the Java side, but use it to decide if a process is a browser
> process or not on the native side.
> 
> Change: Enable the selective JNI registration for all non-browser processes
> on Java side.
> 
> Bug: 674937
> Change-Id: If97814bc5d79cfaa0211e46f785dbab329429d22
> Reviewed-on: https://chromium-review.googlesource.com/552778
> Reviewed-by: Andrew Grieve <agrieve@chromium.org>
> Reviewed-by: Richard Coles <torne@chromium.org>
> Reviewed-by: Yaron Friedman <yfriedman@chromium.org>
> Commit-Queue: Yipeng Wang <yipengw@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#483059}

TBR=yfriedman@chromium.org,torne@chromium.org,agrieve@chromium.org,yipengw@chromium.org

Change-Id: Id2cd35b0a6ac6c3ea9c82a7eec24235d12b2ac37
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 674937
Reviewed-on: https://chromium-review.googlesource.com/553241
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#483203}
[modify] https://crrev.com/4fc72d112fd1b53bd7a0136f0204f182fe3c3310/content/public/android/java/src/org/chromium/content/app/ContentChildProcessServiceDelegate.java

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2665a13c2c0c90a5d9f8ec1215a8af58b0df85c8

commit 2665a13c2c0c90a5d9f8ec1215a8af58b0df85c8
Author: Yipeng Wang <yipengw@chromium.org>
Date: Thu Jun 29 20:14:38 2017

Reland: Enable selective JNI registration for non-browser processes.

Reverted in: If97814bc5d79cfaa0211e46f785dbab329429d22

Reason for reland: changed SurfaceTextureListener class to main dex.

TBR=yfriedman@chromium.org

Bug: 674937
Change-Id: I10eea998628514b1b817a909559b3e97d6f0bd47
Reviewed-on: https://chromium-review.googlesource.com/556360
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Commit-Queue: Yipeng Wang <yipengw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#483461}
[modify] https://crrev.com/2665a13c2c0c90a5d9f8ec1215a8af58b0df85c8/content/public/android/java/src/org/chromium/content/app/ContentChildProcessServiceDelegate.java
[modify] https://crrev.com/2665a13c2c0c90a5d9f8ec1215a8af58b0df85c8/ui/android/java/src/org/chromium/ui/gl/SurfaceTextureListener.java

Is there more work for this or can it be closed?

The points torne@ mentioned in c#4 still need to be resolved 

This fell off my radar, I should probably finish this.

Not entirely sure how to get rid of GetLibraryProcessType() on the native side without adding something else that basically does the same thing (i.e. are we WebView or Chrome?).

torne mentioned having separate entry points above but it's not clear to me how that would work. Don't we need the monochrome lib to have a single exported JNI_OnLoad()?

Monochrome's JNI_OnLoad should be a minimal implementation that only does the important common things, and all the rest of the native initialisation code should be moved to two separate normal JNI functions that can be called by the Java code.

This approach could just be used for Chrome/WebView as well. JNI_OnLoad in all cases could *only* be responsible for JNI registration, which would make it a no-op for webview/monochrome.