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/builder.h b/compiler/optimizing/builder.h
index dce3d9d..6152740 100644
--- a/compiler/optimizing/builder.h
+++ b/compiler/optimizing/builder.h
@@ -19,13 +19,12 @@
 
 #include "base/arena_object.h"
 #include "base/array_ref.h"
-#include "base/macros.h"
 #include "dex/code_item_accessors.h"
 #include "dex/dex_file-inl.h"
 #include "dex/dex_file.h"
 #include "nodes.h"
 
-namespace art HIDDEN {
+namespace art {
 
 class ArtMethod;
 class CodeGenerator;