make float divide-by-zero fatal

Change-Id: I9ba1caa4862bdf9ffc9c0e637bd69cce91fd8468
Reviewed-on: https://skia-review.googlesource.com/c/168740
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
diff --git a/src/shaders/gradients/Sk4fLinearGradient.cpp b/src/shaders/gradients/Sk4fLinearGradient.cpp
index 1575741..cb830f7 100644
--- a/src/shaders/gradients/Sk4fLinearGradient.cpp
+++ b/src/shaders/gradients/Sk4fLinearGradient.cpp
@@ -310,7 +310,7 @@
 
     SkScalar currentAdvance() const {
         SkASSERT(fAdvX >= 0);
-        SkASSERT(fAdvX <= (fInterval->fT1 - fInterval->fT0) / fDx || !std::isfinite(fAdvX));
+        SkASSERT(!std::isfinite(fAdvX) || fAdvX <= (fInterval->fT1 - fInterval->fT0) / fDx);
         return fAdvX;
     }