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/stack_map_test.cc b/compiler/optimizing/stack_map_test.cc
index 62c00b0..d28f09f 100644
--- a/compiler/optimizing/stack_map_test.cc
+++ b/compiler/optimizing/stack_map_test.cc
@@ -18,13 +18,12 @@
 
 #include "art_method.h"
 #include "base/arena_bit_vector.h"
-#include "base/macros.h"
 #include "base/malloc_arena_pool.h"
 #include "stack_map_stream.h"
 
 #include "gtest/gtest.h"
 
-namespace art HIDDEN {
+namespace art {
 
 // Check that the stack mask of given stack map is identical
 // to the given bit vector. Returns true if they are same.