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The default system font can be changed by the user to has
styles. If so, the GetFontFallback should try the
unstyled version.

The primary font was initially tried and failed to Shape
the runs. The unstyled version returned by
GetFallbackFont(...) was not tried since the primary font
has the same name. GetFallbackFonts(...) was able to find
a candidate, but with an higher cost.

To fix the issue, we keep track of the raw SkTypeface
that are tried. ShapeRunWithFonts is using the typeface
to determine the coverage of a run.

This issue was found by adding a DCHECK(false) when
GetFontFallbacks(...) succeed to find a font. It is also
observed in the field in the slow-reports.

bug: 995789
R=robliao@chromium.org

Change-Id: I5b6b7eada35b11306edf0820e5635d5159efdcaf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1994443Reviewed-by: Robert Liao <robliao@chromium.org>
Commit-Queue: Etienne Bergeron <etienneb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#741491}