The following revision refers to this bug:
  https://chromium.googlesource.com/v8/v8.git/+/21db1fafbca21e4f6cc1b5812bb9a821ff8148aa

commit 21db1fafbca21e4f6cc1b5812bb9a821ff8148aa
Author: Ulan Degenbaev <ulan@chromium.org>
Date: Fri Aug 18 09:34:51 2017

[heap] Add histogram counter for incremental marking time per GC cycle.

The name of the histogram is V8.GCIncrementalMarkingSum.

Bug:  chromium:756592 
Change-Id: Ib073e846054550cce8558a3a577a0451e3182407
Reviewed-on: https://chromium-review.googlesource.com/618877
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47422}
[modify] https://crrev.com/21db1fafbca21e4f6cc1b5812bb9a821ff8148aa/src/counters.h
[modify] https://crrev.com/21db1fafbca21e4f6cc1b5812bb9a821ff8148aa/src/heap/gc-tracer.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/818e385a23cc4480e768cc8a3bf4f75b858c00e6

commit 818e385a23cc4480e768cc8a3bf4f75b858c00e6
Author: Ulan Degenbaev <ulan@chromium.org>
Date: Thu Aug 24 13:20:33 2017

Add UMA histogram that tracks V8 incremental marking time per GC cycle.

The name of the histogram is V8.GCIncrementalMarkingSum.

Bug:  chromium:756592 
Change-Id: I441bc2b5498a1b300cd7fc4e422b1275915573c7
Reviewed-on: https://chromium-review.googlesource.com/622830
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#497021}
[modify] https://crrev.com/818e385a23cc4480e768cc8a3bf4f75b858c00e6/tools/metrics/histograms/histograms.xml