Revert of SkPDF: hand SfntlyWrapper::SubsetFont() ttcIndex, not fontName. (patchset...

Revert of SkPDF: hand SfntlyWrapper::SubsetFont() ttcIndex, not fontName. (patchset #3 id:40001 of https://codereview.chromium.org/2258233002/ )

Reason for revert:
forgot to roll sfntly in android!

Original issue's description:
> SkPDF: hand SfntlyWrapper::SubsetFont() ttcIndex, not fontName.
>
> Also, minor code refactoring.
> GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2258233002
>
> Committed: https://skia.googlesource.com/skia/+/fce190647285423bf36c44bca09db78a6af30f9f

TBR=bungeman@google.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review-Url: https://codereview.chromium.org/2296683004