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/optimizing_cfi_test.cc b/compiler/optimizing/optimizing_cfi_test.cc
index a3e4c61..a52031c 100644
--- a/compiler/optimizing/optimizing_cfi_test.cc
+++ b/compiler/optimizing/optimizing_cfi_test.cc
@@ -18,7 +18,6 @@
 #include <vector>
 
 #include "arch/instruction_set.h"
-#include "base/macros.h"
 #include "base/runtime_debug.h"
 #include "cfi_test.h"
 #include "driver/compiler_options.h"
@@ -35,7 +34,7 @@
 
 namespace vixl32 = vixl::aarch32;
 
-namespace art HIDDEN {
+namespace art {
 
 // Run the tests only on host.
 #ifndef ART_TARGET_ANDROID