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

util/mach/mach_extensions_test.cc

 // Copyright 2014 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
 #include "util/mach/mach_extensions.h"
 
 #include "base/mac/scoped_mach_port.h"
 #include "gtest/gtest.h"
 
+namespace crashpad {
+namespace test {
 namespace {
 
-using namespace crashpad;
-
 TEST(MachExtensions, MachThreadSelf) {
   base::mac::ScopedMachSendRight thread_self(mach_thread_self());
   EXPECT_EQ(thread_self, MachThreadSelf());
 }
 
 }  // namespace
+}  // namespace test
+}  // namespace crashpad