The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7519652f89e7c99e1e03e712d5ef8f9e665c756e

commit 7519652f89e7c99e1e03e712d5ef8f9e665c756e
Author: Dominik Röttsches <drott@chromium.org>
Date: Wed Aug 30 05:21:42 2017

Add metrics to measure ratio of variable fonts

Not recording decoding errors as these are already recorded as
kPackageFormatUnknown in FontResource.cpp.

Bug:  757814 
Change-Id: I9861b7d5fe233ecb10a4544134302e0c4a7ca1c8
Reviewed-on: https://chromium-review.googlesource.com/626122
Reviewed-by: Emil A Eklund <eae@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Reviewed-by: Alexei Svitkine (very slow) <asvitkine@chromium.org>
Commit-Queue: Dominik Röttsches <drott@chromium.org>
Cr-Commit-Position: refs/heads/master@{#498371}
[modify] https://crrev.com/7519652f89e7c99e1e03e712d5ef8f9e665c756e/third_party/WebKit/Source/platform/fonts/FontCustomPlatformData.cpp
[modify] https://crrev.com/7519652f89e7c99e1e03e712d5ef8f9e665c756e/third_party/WebKit/Source/platform/fonts/FontCustomPlatformData.h
[modify] https://crrev.com/7519652f89e7c99e1e03e712d5ef8f9e665c756e/tools/metrics/histograms/enums.xml
[modify] https://crrev.com/7519652f89e7c99e1e03e712d5ef8f9e665c756e/tools/metrics/histograms/histograms.xml