move decal_filter_scale inline, walk decal in 32.32

Walking soemtimes in 32.32 and sometimes in 16.16 is leading to small
diffs in https://chromium-review.googlesource.com/c/chromium/src/+/1346729.

I think by walking either consistently will help avoid the problems.
Might as well walk 32.32.

Cq-Include-Trybots: luci.chromium.try:linux-blink-rel
Change-Id: I4bbe8e10655a97367d3b59d203206bc2c2cf55e8
Reviewed-on: https://skia-review.googlesource.com/c/172941
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
2 files changed