Remove DDLTarget tracking from the GrDrawingManager

By making the DDLTask admit that it is using its ddlTarget
we no longer need this tracking in the drawing manager.

Change-Id: I1696ee6c089e4c21abf0781eb7e3b0fa78b3dbb4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/352176
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Adlai Holler <adlai@google.com>
3 files changed