Pin result in SkATan2_255

src/effects/gradients/SkSweepGradient.cpp

Index: src/effects/gradients/SkSweepGradient.cpp
diff --git a/src/effects/gradients/SkSweepGradient.cpp b/src/effects/gradients/SkSweepGradient.cpp
index 24e86d023d78f0b01a7061129632a840a2e36ed7..4c5935158de985a781e459bb87a622458be80955 100644
--- a/src/effects/gradients/SkSweepGradient.cpp
+++ b/src/effects/gradients/SkSweepGradient.cpp
@@ -63,6 +63,9 @@ static unsigned SkATan2_255(float y, float x) {
     static const float g255Over2PI = 40.584510488433314f;
 
     float result = sk_float_atan2(y, x);
+    if (!SkScalarIsFinite(result)) {
+        return 0;
+    }
     if (result < 0) {
         result += 2 * SK_ScalarPI;
     }