Rewrite NaN checks in terms of SkScalarIsNaN()

include/core/SkPoint.h

Index: include/core/SkPoint.h
diff --git a/include/core/SkPoint.h b/include/core/SkPoint.h
index 323c824a1b0e10d523cb2305cd8f0d5de9f4f2a8..4a97391c70e7d71a3029367ce2483a58134b32a5 100644
--- a/include/core/SkPoint.h
+++ b/include/core/SkPoint.h
@@ -357,11 +357,11 @@ struct SK_API SkPoint {
         accum *= fY;
 
         // accum is either NaN or it is finite (zero).
-        SkASSERT(0 == accum || !(accum == accum));
+        SkASSERT(0 == accum || SkScalarIsNaN(accum));
 
         // value==value will be true iff value is not NaN
         // TODO: is it faster to say !accum or accum==accum?
-        return accum == accum;
+        return !SkScalarIsNaN(accum);
     }
 
     /**