Style Change: NULL->nullptr
DOCS_PREVIEW= https://skia.org/?cl=1316233002

Review URL: https://codereview.chromium.org/1316233002
diff --git a/bench/MipMapBench.cpp b/bench/MipMapBench.cpp
index a8156ed..18af1e5 100644
--- a/bench/MipMapBench.cpp
+++ b/bench/MipMapBench.cpp
@@ -29,7 +29,7 @@
 
     void onDraw(const int loops, SkCanvas*) override {
         for (int i = 0; i < loops; i++) {
-            SkMipMap::Build(fBitmap, NULL)->unref();
+            SkMipMap::Build(fBitmap, nullptr)->unref();
         }
     }