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

Review URL: https://codereview.chromium.org/1316233002
diff --git a/gm/spritebitmap.cpp b/gm/spritebitmap.cpp
index 9e1bb87..ceed50a 100644
--- a/gm/spritebitmap.cpp
+++ b/gm/spritebitmap.cpp
@@ -23,7 +23,7 @@
 }
 
 static void draw_2_bitmaps(SkCanvas* canvas, const SkBitmap& bm, bool doClip,
-                           int dx, int dy, SkImageFilter* filter = NULL) {
+                           int dx, int dy, SkImageFilter* filter = nullptr) {
     SkAutoCanvasRestore acr(canvas, true);
     SkPaint paint;