SkPDF: Subset Type3 (fallback) font

Motivation: significant file-size reduction.

Also: SkPDFFont::subsetFont() returns a sk_sp<SkPDFObject>
rather than a SkPDFFont*.

SkPDFType3Font constructor no longer populates font info;
relies on subsetting.

SkPDFFont::Create is easier to read

Also: SkPDFType3Font are scaled by emSize rather than 1000.

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2231483002

Review-Url: https://codereview.chromium.org/2231483002
4 files changed