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

snapshot/cpu_context_mac_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 "snapshot/cpu_context_mac.h"
 
 #include <mach/mach.h>
 
 #include "gtest/gtest.h"
 
+namespace crashpad {
+namespace test {
 namespace {
 
-using namespace crashpad;
-
 #if defined(ARCH_CPU_X86_FAMILY)
 
 TEST(CPUContextMac, InitializeContextX86) {
   x86_thread_state32_t x86_thread_state32 = {};
   x86_float_state32_t x86_float_state32 = {};
   x86_debug_state32_t x86_debug_state32 = {};
   x86_thread_state32.__eax = 1;
   x86_float_state32.__fpu_ftw = 2;
   x86_debug_state32.__dr0 = 3;
 
@@ skipping 375 matching lines @@
         &x86_debug_state64);
     EXPECT_EQ(10u, cpu_context_x86_64.rax);
     EXPECT_EQ(11u, cpu_context_x86_64.fxsave.ftw);
     EXPECT_EQ(12u, cpu_context_x86_64.dr0);
   }
 }
 
 #endif
 
 }  // namespace
+}  // namespace test
+}  // namespace crashpad