Experimental text editor: factor out Editor class.

Change-Id: Ie3ab5566b66f8255097001d015b39ca650cc0f20
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/210920
Commit-Queue: Hal Canary <halcanary@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
Auto-Submit: Hal Canary <halcanary@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
4 files changed