The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8ff4d2836039766ef72205144bb5f538d2712116

commit 8ff4d2836039766ef72205144bb5f538d2712116
Author: drott <drott@chromium.org>
Date: Thu Apr 27 08:41:39 2017

Test OpenType rvrn Required Variation Alternates

The rvrn feature [1] and the FeatureVariations part of GSUB describe
single glyph substitutions dependent on variation axis values. In order
to add test coverage for this, the variabletest_box.ttf font was
extended to have two new glyphs for r and R respectively displaying
"rvrn base" and "rvrn subst" (for "substituted"). When a new axis
'fvtt', ranging from 0 to 10, is set to >= 5, the rvrn_base glyph is
replaced with the rvrn_subst glyph. This enables creating a reftest of
where a lowercase r with font-variation-settings: "fvtt" 10; must match
the uppercase R, which selects the "rvrn_subst" glyph explicitly.

[1] https://www.microsoft.com/typography/OTSpec/features_pt.htm#rvrn

BUG= 715900 

Review-Url: https://codereview.chromium.org/2845953002
Cr-Commit-Position: refs/heads/master@{#467621}

[modify] https://crrev.com/8ff4d2836039766ef72205144bb5f538d2712116/third_party/WebKit/LayoutTests/NeverFixTests
[add] https://crrev.com/8ff4d2836039766ef72205144bb5f538d2712116/third_party/WebKit/LayoutTests/fast/text/variable-fonts/variable-gsub-expected.html
[add] https://crrev.com/8ff4d2836039766ef72205144bb5f538d2712116/third_party/WebKit/LayoutTests/fast/text/variable-fonts/variable-gsub.html
[modify] https://crrev.com/8ff4d2836039766ef72205144bb5f538d2712116/third_party/WebKit/LayoutTests/http/tests/resources/variabletest_box.ttf