Clean up ZygoteHooks stack walking slightly.

Test: Build and run marlin with libartd.so
Change-Id: I4a67935c5c7270636085c3ee12db0ebc1798a89e
diff --git a/runtime/non_debuggable_classes.h b/runtime/non_debuggable_classes.h
index 0c94dc0..e1b5633 100644
--- a/runtime/non_debuggable_classes.h
+++ b/runtime/non_debuggable_classes.h
@@ -21,21 +21,16 @@
 
 #include "base/mutex.h"
 #include "jni.h"
-#include "obj_ptr.h"
 
 namespace art {
 
-namespace mirror {
-class Class;
-}  // namespace mirror
-
 struct NonDebuggableClasses {
  public:
   static const std::vector<jclass>& GetNonDebuggableClasses() {
     return non_debuggable_classes;
   }
 
-  static void AddNonDebuggableClass(ObjPtr<mirror::Class> klass)
+  static void AddNonDebuggableClass(jclass klass)
       REQUIRES_SHARED(Locks::mutator_lock_);
 
  private: