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The histogram definitions were landed in Skia at:
https://skia-review.googlesource.com/c/skia/+/329963
https://skia-review.googlesource.com/c/skia/+/329776

The key change that enables these histograms is the including of
skia_historgram.h in SkUserConfig.h. This was disabled (by removing the
include) about 4 years ago because of "issues" but there is no bug
associated so its not clear what those issues are. The disable CL says
that "Skia histograms are generating invalid data". Building and running
locally I don't seem to get an errors being reported by chrome, and
the values in chrome://histograms all looks correct.

The plan here is that once this lands we will monitor the add metrics
for statistical anomalies to validate whether the previous errors from
four years ago have been fixed.

This also adds support for additional macros to be used.

Bug: skia:10871
Change-Id: Ic7447ecc66d882df7e1b6e5e1f4088a50ce56921
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2505594
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Jonathan Backer <backer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#826753}