The following revision refers to this bug:
  https://chromium.googlesource.com/v8/v8.git/+/fb436a5e153876c55b725d04db582ad37b225d83

commit fb436a5e153876c55b725d04db582ad37b225d83
Author: Hannes Payer <hpayer@chromium.org>
Date: Thu May 24 18:25:32 2018

Adding an API to enable and disable the memory savings mode.

Bug: chromium:846360
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I5376d4f6f9c8df768d60c63e0a767bf41b51b8b3
Reviewed-on: https://chromium-review.googlesource.com/1071531
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53345}
[modify] https://crrev.com/fb436a5e153876c55b725d04db582ad37b225d83/include/v8.h
[modify] https://crrev.com/fb436a5e153876c55b725d04db582ad37b225d83/src/api.cc
[modify] https://crrev.com/fb436a5e153876c55b725d04db582ad37b225d83/src/counters.h
[modify] https://crrev.com/fb436a5e153876c55b725d04db582ad37b225d83/src/heap/heap.cc
[modify] https://crrev.com/fb436a5e153876c55b725d04db582ad37b225d83/src/isolate.cc
[modify] https://crrev.com/fb436a5e153876c55b725d04db582ad37b225d83/src/isolate.h
[modify] https://crrev.com/fb436a5e153876c55b725d04db582ad37b225d83/test/cctest/test-api.cc

We'll use this bug to track field trials of Site Isolation + memory savings mode, to see what the impact is.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6e3d725c21390af9a30d0cc98b0d1ac34b820ee9

commit 6e3d725c21390af9a30d0cc98b0d1ac34b820ee9
Author: Robert Sesek <rsesek@chromium.org>
Date: Wed Jun 06 14:38:02 2018

Add an experiment for enabling V8's memory savings mode on Android.

This feature works in conjunction with --site-per-process. When a renderer
process has only subframes, Blink's main thread isolate will be put
into a memory savings mode. If a main frame is created in the process,
the isolate will be taken out of memory savings mode for as long as a main
frame exists.

Bug: 846360
Change-Id: I09c362cce648b734fb01907a5ad758f0bdb7f752
Reviewed-on: https://chromium-review.googlesource.com/1076954
Reviewed-by: Brian White <bcwhite@chromium.org>
Reviewed-by: Nasko Oskov <nasko@chromium.org>
Commit-Queue: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#564881}
[modify] https://crrev.com/6e3d725c21390af9a30d0cc98b0d1ac34b820ee9/content/browser/renderer_host/render_process_host_impl.cc
[modify] https://crrev.com/6e3d725c21390af9a30d0cc98b0d1ac34b820ee9/content/browser/service_worker/embedded_worker_test_helper.cc
[modify] https://crrev.com/6e3d725c21390af9a30d0cc98b0d1ac34b820ee9/content/common/renderer.mojom
[modify] https://crrev.com/6e3d725c21390af9a30d0cc98b0d1ac34b820ee9/content/public/common/content_features.cc
[modify] https://crrev.com/6e3d725c21390af9a30d0cc98b0d1ac34b820ee9/content/public/common/content_features.h
[modify] https://crrev.com/6e3d725c21390af9a30d0cc98b0d1ac34b820ee9/content/renderer/BUILD.gn
[add] https://crrev.com/6e3d725c21390af9a30d0cc98b0d1ac34b820ee9/content/renderer/low_memory_mode_controller.cc
[add] https://crrev.com/6e3d725c21390af9a30d0cc98b0d1ac34b820ee9/content/renderer/low_memory_mode_controller.h
[add] https://crrev.com/6e3d725c21390af9a30d0cc98b0d1ac34b820ee9/content/renderer/low_memory_mode_controller_unittest.cc
[modify] https://crrev.com/6e3d725c21390af9a30d0cc98b0d1ac34b820ee9/content/renderer/render_frame_impl.cc
[modify] https://crrev.com/6e3d725c21390af9a30d0cc98b0d1ac34b820ee9/content/renderer/render_thread_impl.cc
[modify] https://crrev.com/6e3d725c21390af9a30d0cc98b0d1ac34b820ee9/content/renderer/render_thread_impl.h
[modify] https://crrev.com/6e3d725c21390af9a30d0cc98b0d1ac34b820ee9/content/test/BUILD.gn
[modify] https://crrev.com/6e3d725c21390af9a30d0cc98b0d1ac34b820ee9/testing/variations/fieldtrial_testing_config.json
[modify] https://crrev.com/6e3d725c21390af9a30d0cc98b0d1ac34b820ee9/tools/metrics/histograms/histograms.xml

Thanks for the CL in #c5!  I can put together a CL configuring the field trail for this functionality (it probably needs to be coordinated with the current site-per-process trials and might be blocked by another in-flight field-trial-config-CL in this area).

Sounds good! Thanks for volunteering to handle the field trial setup.