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_compiler_stats.h b/compiler/optimizing/optimizing_compiler_stats.h
index 6a69a33..83dbef7 100644
--- a/compiler/optimizing/optimizing_compiler_stats.h
+++ b/compiler/optimizing/optimizing_compiler_stats.h
@@ -26,9 +26,8 @@
 
 #include "base/atomic.h"
 #include "base/globals.h"
-#include "base/macros.h"
 
-namespace art HIDDEN {
+namespace art {
 
 enum class MethodCompilationStat {
   kAttemptBytecodeCompilation = 0,