Update DDL test harness to use backendTextures to back tiles

This better matches Chrome's use of DDLs.

With path, image, and text draws stripped out, here is the perf impact of this change:

           before CL   after CL
w/ DDLs      7.792      1.038
w/o DDLs     0.800      0.876

This perf improvement (in the DDL case) is from backend texture wrapping SkSurfaces being created w/o initialization. The prior method of SkSurface creation was resulting in double clearing of all the surfaces.

This perf improvement won't be seen by Chrome since they've always being using wrapped backend texture SkSurfaces.

TBR=bsalomon@google.com
Change-Id: Ice3993ca125fce37804e58c353c265cf659dbe2f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/283456
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
5 files changed