Not sure I understand the context, but you might want to use the functions in histogram_functions.h instead of the macros.

Note that the macros cache their result, so the string passed to the macro has to be constant.

Thanks!  That's exactly what I need.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/90b52ca347662faa95b0a273952f480575e1840a

commit 90b52ca347662faa95b0a273952f480575e1840a
Author: Ben Kelly <wanderview@chromium.org>
Date: Sat Dec 01 00:09:58 2018

CacheStorage: Refactor scheduler UMA recording to reduce code size.

Previously CacheStorage used some very large macros to record a number
of scheduler related histograms.  These macros produce a lot of code
bloat and are difficult to read.  This CL addresses those issues by
replacing the macros with functions.

Bug:  909894 
Change-Id: Icc3adc91d72de2aeaac0f927c13f3e2bfb557e77
Reviewed-on: https://chromium-review.googlesource.com/c/1357400
Commit-Queue: Ben Kelly <wanderview@chromium.org>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612864}
[modify] https://crrev.com/90b52ca347662faa95b0a273952f480575e1840a/content/browser/cache_storage/cache_storage_histogram_utils.cc
[modify] https://crrev.com/90b52ca347662faa95b0a273952f480575e1840a/content/browser/cache_storage/cache_storage_histogram_utils.h
[modify] https://crrev.com/90b52ca347662faa95b0a273952f480575e1840a/content/browser/cache_storage/cache_storage_operation.cc
[modify] https://crrev.com/90b52ca347662faa95b0a273952f480575e1840a/content/browser/cache_storage/cache_storage_operation.h
[modify] https://crrev.com/90b52ca347662faa95b0a273952f480575e1840a/content/browser/cache_storage/cache_storage_scheduler.cc