Revert "Make compiler/optimizing/ symbols hidden."

This reverts commit e2727154f25e0db9a5bb92af494d8e47b181dfcf.

Reason for revert: Breaks ASAN tests (ODR violation).
Bug: 142365358

Change-Id: I38103d74a1297256c81d90872b6902ff1e9ef7a4
diff --git a/compiler/optimizing/constant_folding_test.cc b/compiler/optimizing/constant_folding_test.cc
index 2730fc7..74d9d3a 100644
--- a/compiler/optimizing/constant_folding_test.cc
+++ b/compiler/optimizing/constant_folding_test.cc
@@ -17,8 +17,6 @@
 #include <functional>
 
 #include "constant_folding.h"
-
-#include "base/macros.h"
 #include "dead_code_elimination.h"
 #include "driver/compiler_options.h"
 #include "graph_checker.h"
@@ -27,7 +25,7 @@
 
 #include "gtest/gtest.h"
 
-namespace art HIDDEN {
+namespace art {
 
 /**
  * Fixture class for the constant folding and dce tests.