Ensure the GC visits Obsolete Methods

We were previously not visiting obsolete methods during GCs. This
could lead to the use of stale pointers.

Bug: 36335999
Test: ./test/testrunner/testrunner.py --host --interp-ac --gcstress -j40

Change-Id: I2b5c7c75b29f9037204a860501fcdb78104b5e7a
diff --git a/runtime/mirror/class_ext-inl.h b/runtime/mirror/class_ext-inl.h
new file mode 100644
index 0000000..feaac85
--- /dev/null
+++ b/runtime/mirror/class_ext-inl.h
@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_RUNTIME_MIRROR_CLASS_EXT_INL_H_
+#define ART_RUNTIME_MIRROR_CLASS_EXT_INL_H_
+
+#include "class_ext.h"
+
+#include "art_method-inl.h"
+
+namespace art {
+namespace mirror {
+
+template<ReadBarrierOption kReadBarrierOption, class Visitor>
+void ClassExt::VisitNativeRoots(Visitor& visitor, PointerSize pointer_size) {
+  ObjPtr<PointerArray> arr(GetObsoleteMethods<kDefaultVerifyFlags, kReadBarrierOption>());
+  if (arr.IsNull()) {
+    return;
+  }
+  int32_t len = arr->GetLength();
+  for (int32_t i = 0; i < len; i++) {
+    ArtMethod* method = arr->GetElementPtrSize<ArtMethod*,
+                                               kDefaultVerifyFlags,
+                                               kReadBarrierOption>(i, pointer_size);
+    if (method != nullptr) {
+      method->VisitRoots<kReadBarrierOption>(visitor, pointer_size);
+    }
+  }
+}
+
+}  // namespace mirror
+}  // namespace art
+
+#endif  // ART_RUNTIME_MIRROR_CLASS_EXT_INL_H_