Reland "SkShaper JSON output with cluster visualization"

This is a reland of 53610832a04157e4edf18347c3e69ddd9d799e3f

Fixes conversion of size_t to int.

Original change's description:
> 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>

Change-Id: I712293c4820eb23234d64fa019d28bac8b105637
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/211986
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Herb Derby <herb@google.com>
6 files changed