Don't erase child optimization flags

The matrix effect and the device-space effect only change the coordinates
the child FP is evaluated at. Any optimization based on the child's color
behavior is still valid.

Change-Id: Ib92fb0c627ec18c7eac85e9d4162e47866694d4f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/298065
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
3 files changed