A GrSlug encapsulates an SkTextBlob at a certain origin, using a
given paint. Once a blob is converted to a slug, it can be drawn
through a canvas and will obey the canvas's mapping and clipping.
The glyphs encoded as mask will be transformed using bi-linear
interpolation. The other glyphs type will draw as they normally
would. This allows drawing an SkTextBlob using the original
glyph data from the cache.
Bug: chromium:1254726
Change-Id: I1b42c94966d22865922ce991ae6ed13b51360618
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/471157
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Herb Derby <herb@google.com>
