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

Review URL: https://codereview.chromium.org/1316233002
diff --git a/gm/astcbitmap.cpp b/gm/astcbitmap.cpp
index 8ee7746..bc5e1e9 100644
--- a/gm/astcbitmap.cpp
+++ b/gm/astcbitmap.cpp
@@ -70,7 +70,7 @@
                 }
 
                 SkAutoTUnref<SkData> fileData(SkData::NewFromFileName(filename.c_str()));
-                if (NULL == fileData) {
+                if (nullptr == fileData) {
                     SkDebugf("Could not open the file. Did you forget to set the resourcePath?\n");
                     return;
                 }