Now that there may be multiple font managers in a process the typeface
ids must be unique across all typefaces, not just unique within a font
manager. If two typefaces have the same id there will be issues in the
glyph cache. All existing font managers were already doing this by
calling SkFontCache::NewFontID, so centralize this in SkTypeface.
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2147733002
Review-Url: https://codereview.chromium.org/2147733002
e3aea10428