Fix memory leak in logging-unittest.

test/unittests/base/logging-unittest.cc

Index: test/unittests/base/logging-unittest.cc
diff --git a/test/unittests/base/logging-unittest.cc b/test/unittests/base/logging-unittest.cc
index 93de78b2c9b508d351822b2eead0365d4a655b91..5c0ca007c4d0524722194d468bff9aaaec733437 100644
--- a/test/unittests/base/logging-unittest.cc
+++ b/test/unittests/base/logging-unittest.cc
@@ -25,6 +25,7 @@ namespace {
     std::string* error_message =                                           \
         Check##NAME##Impl<decltype(lhs), decltype(rhs)>((lhs), (rhs), ""); \
     EXPECT_NE(nullptr, error_message);                                     \
+    delete error_message;                                                  \
   }
 
 }  // namespace