Don’t use using directives (“using namespace”) in tests

util/mach/mach_message_server_test.cc

Index: util/mach/mach_message_server_test.cc
diff --git a/util/mach/mach_message_server_test.cc b/util/mach/mach_message_server_test.cc
index 3d0d8bd76903e74177a03e0f0cc7a00b76c3384e..f732bbc29df4b3d3d078f6679c888a1e0677cc0a 100644
--- a/util/mach/mach_message_server_test.cc
+++ b/util/mach/mach_message_server_test.cc
@@ -25,11 +25,10 @@
 #include "util/test/mac/mach_errors.h"
 #include "util/test/mac/mach_multiprocess.h"
 
+namespace crashpad {
+namespace test {
 namespace {
 
-using namespace crashpad;
-using namespace crashpad::test;
-
 class TestMachMessageServer : public MachMessageServer::Interface,
                               public MachMultiprocess {
  public:
@@ -845,3 +844,5 @@ TEST(MachMessageServer, LargeExpected) {
 }
 
 }  // namespace
+}  // namespace test
+}  // namespace crashpad