Fix 616-cha-unloading.

Consider cases of implicit arena reuse to prevent false positives.

Test: 616-cha-unloading

Change-Id: Ia1755fb66167279c08dd9ba59813402e798c0b79
diff --git a/runtime/class_linker.cc b/runtime/class_linker.cc
index 3025818..ba90c17 100644
--- a/runtime/class_linker.cc
+++ b/runtime/class_linker.cc
@@ -8917,6 +8917,15 @@
   }
 }
 
+void ClassLinker::VisitAllocators(AllocatorVisitor* visitor) const {
+  for (const ClassLoaderData& data : class_loaders_) {
+    LinearAlloc* alloc = data.allocator;
+    if (alloc != nullptr && !visitor->Visit(alloc)) {
+        break;
+    }
+  }
+}
+
 void ClassLinker::InsertDexFileInToClassLoader(ObjPtr<mirror::Object> dex_file,
                                                ObjPtr<mirror::ClassLoader> class_loader) {
   DCHECK(dex_file != nullptr);