Add new DM via, "ddl2" which records/draws DDLs for each test twice.

Clears between the two DDL runs.

Also, fix up proxy unique key checks in GrSurfaceProxy.

Change-Id: I492e791ebc57a42063f3b828c10d8bf5fee70b1b
Reviewed-on: https://skia-review.googlesource.com/c/178262
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
4 files changed