Visit class roots from ClassLoader::VisitReferences

This causes the classes of a class loader to get marked when that
class loader gets marked instead of during class root visiting.

Bug: 22720414

Change-Id: If53f042aff1d9f7bf94ecbe6886601edda029b7d
diff --git a/runtime/mirror/class.h b/runtime/mirror/class.h
index 513ab37..dc60a38 100644
--- a/runtime/mirror/class.h
+++ b/runtime/mirror/class.h
@@ -236,6 +236,15 @@
     SetAccessFlags(flags | kAccClassIsStringClass);
   }
 
+  ALWAYS_INLINE bool IsClassLoaderClass() SHARED_REQUIRES(Locks::mutator_lock_) {
+    return (GetField32(AccessFlagsOffset()) & kAccClassIsClassLoaderClass) != 0;
+  }
+
+  ALWAYS_INLINE void SetClassLoaderClass() SHARED_REQUIRES(Locks::mutator_lock_) {
+    uint32_t flags = GetField32(OFFSET_OF_OBJECT_MEMBER(Class, access_flags_));
+    SetAccessFlags(flags | kAccClassIsClassLoaderClass);
+  }
+
   // Returns true if the class is abstract.
   ALWAYS_INLINE bool IsAbstract() SHARED_REQUIRES(Locks::mutator_lock_) {
     return (GetAccessFlags() & kAccAbstract) != 0;