Rewrite NaN checks in terms of SkScalarIsNaN()

include/core/SkRect.h

Index: include/core/SkRect.h
diff --git a/include/core/SkRect.h b/include/core/SkRect.h
index 394e45d4ca3866ce4c000af3dd05df399554da2d..0038c7c2fa2bbe3ad4fa14f403151ef9553063c6 100644
--- a/include/core/SkRect.h
+++ b/include/core/SkRect.h
@@ -455,11 +455,11 @@ struct SK_API SkRect {
         accum *= fBottom;
 
         // 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);
     }
 
     SkScalar    x() const { return fLeft; }