Revert "Remove use of integers for atlas indexing"

This reverts commit 3a8f345cf5689c6e1f22e852acfde4b8b1e5ba42.

Reason for revert: Text not drawing.

Original change's description:
> Remove use of integers for atlas indexing
> 
> Bug: skia:
> Change-Id: I7c29e90de6531a35c415f0338e23c176a7293040
> Reviewed-on: https://skia-review.googlesource.com/c/171233
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Jim Van Verth <jvanverth@google.com>

TBR=jvanverth@google.com,bsalomon@google.com

Change-Id: I7da2f34636c7871dfe2b064d9fa511d34d316827
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/c/171531
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
3 files changed