Move compiler cctests into v8::internal::compiler namespace.

test/cctest/compiler/test-simplified-lowering.cc

Index: test/cctest/compiler/test-simplified-lowering.cc
diff --git a/test/cctest/compiler/test-simplified-lowering.cc b/test/cctest/compiler/test-simplified-lowering.cc
index d0bed8422095577c2db70c2e8670da1801422169..20bfc0f7315f8e381026206fe3804b0053193281 100644
--- a/test/cctest/compiler/test-simplified-lowering.cc
+++ b/test/cctest/compiler/test-simplified-lowering.cc
@@ -29,8 +29,9 @@
 #include "test/cctest/compiler/graph-builder-tester.h"
 #include "test/cctest/compiler/value-helper.h"
 
-using namespace v8::internal;
-using namespace v8::internal::compiler;
+namespace v8 {
+namespace internal {
+namespace compiler {
 
 template <typename ReturnType>
 class SimplifiedLoweringTester : public GraphBuilderTester<ReturnType> {
@@ -2006,3 +2007,7 @@ TEST(PhiRepresentation) {
     CHECK_EQ(d.expected, OpParameter<MachineType>(phi));
   }
 }
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8