fill the layer if there is a backdrop filter

Bug: skia:8783
Change-Id: I92448382117b1bd05a0ad5cf7ecd72181631389b
Reviewed-on: https://skia-review.googlesource.com/c/194601
Auto-Submit: Mike Reed <reed@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
1 file changed