Plumb strike through the common code.

Plump the strike calculated in the calling code through
drawGlyphRunAsBMPWithPathFallback. This is in anticipation
of calculating the cache in drawGlyphRunAsBMPWithPathFallback.

* Add getDescriptor to SkStrikeInterface.

Change-Id: I904cdb51f60443cabc9dc41ac246b1fe0c725c85
Reviewed-on: https://skia-review.googlesource.com/c/191285
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Herb Derby <herb@google.com>
5 files changed