Add a GM for SkShadowUtils and fix a few issues.

1) Transform the path center to device space before computing the shadow offset.

2) Modulate the shadow color by the color filter's output color.

3) Make the scale of path points in the spot tessellator be relative to the path centroid.

4) Clamp the shadow alphas at 1.

Change-Id: I480476df79b959f11c1eca0ba2a49a134d355cbb
Reviewed-on: https://skia-review.googlesource.com/7860
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/gn/gm.gni b/gn/gm.gni
index 4b6dbf90cd..38e50b57ec 100644
--- a/gn/gm.gni
+++ b/gn/gm.gni
@@ -247,6 +247,7 @@ gm_sources = [
   "$_gm/shadertext3.cpp",
   "$_gm/shadowmaps.cpp",
   "$_gm/shadows.cpp",
+  "$_gm/shadowutils.cpp",
   "$_gm/shallowgradient.cpp",
   "$_gm/shapes.cpp",
   "$_gm/showmiplevels.cpp",