SkPDF: less tolerance for small circles

BUG=chromium:772953
Change-Id: I9452ac8ad66ab8be26a9388f8c85a1f0e61bd392
Reviewed-on: https://skia-review.googlesource.com/75960
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
diff --git a/gn/gm.gni b/gn/gm.gni
index 22d562f..ad542fb 100644
--- a/gn/gm.gni
+++ b/gn/gm.gni
@@ -60,6 +60,7 @@
   "$_gm/bug615686.cpp",
   "$_gm/cgm.c",
   "$_gm/cgms.cpp",
+  "$_gm/circle_sizes.cpp",
   "$_gm/circles.cpp",
   "$_gm/circulararcs.cpp",
   "$_gm/circularclips.cpp",