A simple gradient test

Change-Id: Ic3e53f7eab747f63641e0eb6a1c73ad0833acef6
Reviewed-on: https://skia-review.googlesource.com/8158
Reviewed-by: Matt Sarett <msarett@google.com>
Commit-Queue: Tenghui Zhu <ztenghui@google.com>
diff --git a/gn/gm.gni b/gn/gm.gni
index 09a7963..be3a482 100644
--- a/gn/gm.gni
+++ b/gn/gm.gni
@@ -279,6 +279,7 @@
   "$_gm/surface.cpp",
   "$_gm/tablecolorfilter.cpp",
   "$_gm/tallstretchedbitmaps.cpp",
+  "$_gm/testgradient.cpp",
   "$_gm/texdata.cpp",
   "$_gm/textblob.cpp",
   "$_gm/textblobblockreordering.cpp",