ccpr: Remove GrCCDrawPathsOp's back-pointer into CCPR

Bug: skia:7988
Change-Id: Ia05173e90fa2cda28de6ae2a9aaee577eaf4bc65
Reviewed-on: https://skia-review.googlesource.com/129621
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
5 files changed