Added in Radial Shadows

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2311223004

Review-Url: https://codereview.chromium.org/2311223004
diff --git a/gm/shadowmaps.cpp b/gm/shadowmaps.cpp
index acbf275..b675aca 100644
--- a/gm/shadowmaps.cpp
+++ b/gm/shadowmaps.cpp
@@ -84,8 +84,8 @@
     }
 
 protected:
-    constexpr int kWidth = 400;
-    constexpr int kHeight = 400;
+    static constexpr int kWidth = 400;
+    static constexpr int kHeight = 400;
 
     SkString onShortName() override {
         return SkString("shadowmaps");