Upstream, cl/199129756

Add printer for std::nullptr_t, addressing https://github.com/google/googletest/issues/1616

googletest/include/gtest/gtest-printers.h

@@ -636,6 +636,10 @@ inline void PrintTo(absl::string_view sp, ::std::ostream* os) {
 }
 #endif  // GTEST_HAS_ABSL
 
+#if GTEST_LANG_CXX11
+inline void PrintTo(std::nullptr_t, ::std::ostream* os) { *os << "(nullptr)"; }
+#endif  // GTEST_LANG_CXX11
+
 #if GTEST_HAS_TR1_TUPLE || GTEST_HAS_STD_TUPLE_
 // Helper function for printing a tuple.  T must be instantiated with
 // a tuple type.

googletest/test/gtest-printers_test.cc

@@ -1115,6 +1115,12 @@ TEST(PrintStdTupleTest, NestedTuple) {
 
 #endif  // GTEST_LANG_CXX11
 
+#if GTEST_LANG_CXX11
+TEST(PrintNullptrT, Basic) {
+  EXPECT_EQ("(nullptr)", Print(nullptr));
+}
+#endif  // GTEST_LANG_CXX11
+
 // Tests printing user-defined unprintable types.
 
 // Unprintable types in the global namespace.