Add a GM to test out odd matrix draws (take 2)

TBR=bsalomon@google.com
Bug: skia:7075
Change-Id: I87efa058916fe0305b57eb4dd14b479e8a8d2c6d
Reviewed-on: https://skia-review.googlesource.com/65507
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
diff --git a/gn/gm.gni b/gn/gm.gni
index 3ccf8a8..441c041 100644
--- a/gn/gm.gni
+++ b/gn/gm.gni
@@ -131,6 +131,7 @@
   "$_gm/filterbug.cpp",
   "$_gm/filterfastbounds.cpp",
   "$_gm/filterindiabox.cpp",
+  "$_gm/flippity.cpp",
   "$_gm/fontcache.cpp",
   "$_gm/fontmgr.cpp",
   "$_gm/fontscaler.cpp",