Upcall support for x86-64.

Sufficient to pass jni_internal_test.

Change-Id: Ia0d9b8241ab8450e04765b9c32eb6dc8fc1a8733
diff --git a/runtime/runtime.h b/runtime/runtime.h
index 159de2e..223b8d5 100644
--- a/runtime/runtime.h
+++ b/runtime/runtime.h
@@ -429,6 +429,10 @@
     return callee_save_methods_[type];
   }
 
+  static size_t GetCalleeSaveMethodOffset(CalleeSaveType type) {
+    return OFFSETOF_MEMBER(Runtime, callee_save_methods_[type]);
+  }
+
   void SetCalleeSaveMethod(mirror::ArtMethod* method, CalleeSaveType type);
 
   mirror::ArtMethod* CreateCalleeSaveMethod(InstructionSet instruction_set,