SkShaper JSON output with cluster visualization

A simple JSON output for diagnostic purposes.
If the run is not 1:1 code points to glyphs, then
break the run into clusters.

Change-Id: I06980e0bac2cdca8a69b5b5ba0759a021fd4eb3b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/209740
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Julia Lavrova <jlavrova@google.com>
6 files changed