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

mojo/public/cpp/environment/tests/logging_unittest.cc

Index: mojo/public/cpp/environment/tests/logging_unittest.cc
diff --git a/mojo/public/cpp/environment/tests/logging_unittest.cc b/mojo/public/cpp/environment/tests/logging_unittest.cc
index 38bf33681f67a59ac519772a76681632d67fa5c6..45f527e2400cec2db45d52906b649e11881fd818 100644
--- a/mojo/public/cpp/environment/tests/logging_unittest.cc
+++ b/mojo/public/cpp/environment/tests/logging_unittest.cc
@@ -31,7 +31,7 @@ bool DcheckTestHelper(bool* was_called) {
 
 class LoggingTest : public testing::Test {
  public:
-  LoggingTest() : environment_(NULL, &kMockLogger) {
+  LoggingTest() : environment_(nullptr, &kMockLogger) {
     minimum_log_level_ = MOJO_LOG_LEVEL_INFO;
     ResetMockLogger();
   }