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In order to avoid rendering inconsistencies between static and variable
fonts on Windows, run variable fonts through Skia's DWrite backend when
the system's DWrite version supports it.

As the test, use a default typeface to probe and ask for the variation
axis parameters of the current instance. If Skia return -1, it means, it
was unable to access the API for retrieving variations axes
information. If that's the case, we need to use FreeType, otherwise use
DWrite.

While we do not have bot coverage for Windows 10 RS3 ourselves, Skia
does test DWrite variable font support, so I believe it's okay to land
that, our own bot coverage is tracked in issue 953520.

Bug: 953447
Change-Id: I9684f92004531d6bafef33aefafa3894e4c46203
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1569947Reviewed-by: Emil A Eklund <eae@chromium.org>
Commit-Queue: Dominik Röttsches <drott@chromium.org>
Cr-Commit-Position: refs/heads/master@{#651797}