Add visibility attributes in runtime/c*

Bug: 260881207
Test: presubmit
Test: abtd app_compat_drm
Test: abtd app_compat_top_100
Test: abtd app_compat_banking
Change-Id: Id729aca1d8b6d003ff3e9755112f3283e9f2b507
diff --git a/runtime/class_loader_context.h b/runtime/class_loader_context.h
index cfb0457..6b819f4 100644
--- a/runtime/class_loader_context.h
+++ b/runtime/class_loader_context.h
@@ -23,19 +23,20 @@
 
 #include "arch/instruction_set.h"
 #include "base/dchecked_vector.h"
+#include "base/macros.h"
 #include "dex/dex_file.h"
 #include "handle_scope.h"
 #include "mirror/class_loader.h"
 #include "oat/oat_file.h"
 #include "scoped_thread_state_change.h"
 
-namespace art {
+namespace art HIDDEN {
 
 class DexFile;
 class OatFile;
 
 // Utility class which holds the class loader context used during compilation/verification.
-class ClassLoaderContext {
+class EXPORT ClassLoaderContext {
  public:
   enum class VerificationResult {
     kVerifies,