Mojo: NULL -> nullptr in mojo/public/cpp outside of bindings.

mojo/public/cpp/test_support/lib/test_support.cc

Index: mojo/public/cpp/test_support/lib/test_support.cc
diff --git a/mojo/public/cpp/test_support/lib/test_support.cc b/mojo/public/cpp/test_support/lib/test_support.cc
index 55a3dcc702460c9aa7a54da798e1a76f3ee96e36..0b6035b9c2dec828d574ce86da39d9a0c41bd1e8 100644
--- a/mojo/public/cpp/test_support/lib/test_support.cc
+++ b/mojo/public/cpp/test_support/lib/test_support.cc
@@ -14,7 +14,7 @@ std::vector<std::string> EnumerateSourceRootRelativeDirectory(
   char** names = MojoTestSupportEnumerateSourceRootRelativeDirectory(
       relative_path.c_str());
   std::vector<std::string> results;
-  for (char** ptr = names; *ptr != NULL; ++ptr) {
+  for (char** ptr = names; *ptr != nullptr; ++ptr) {
     results.push_back(*ptr);
     free(*ptr);
   }