Remove single use of commonFilterLoop

There is only one use of commonFilterLoop in
prepareForDrawingMasksCPU. Inline commonFilterLoop and remove it.

Bug: skia:14065
Change-Id: Ied85e257c42d76a799794e5444d6986799cf8ff3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/635497
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
2 files changed