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

Review URL: https://codereview.chromium.org/1316233002
diff --git a/gm/imagemagnifier.cpp b/gm/imagemagnifier.cpp
index ac1941c..2bf2226 100644
--- a/gm/imagemagnifier.cpp
+++ b/gm/imagemagnifier.cpp
@@ -38,7 +38,7 @@
                                  SkIntToScalar(WIDTH / 2),
                                  SkIntToScalar(HEIGHT / 2)),
                 100))->unref();
-        canvas->saveLayer(NULL, &filterPaint);
+        canvas->saveLayer(nullptr, &filterPaint);
         const char* str = "The quick brown fox jumped over the lazy dog.";
         SkRandom rand;
         for (int i = 0; i < 25; ++i) {