Tidy MethodProtoHelper.

Move to place of only use, class_linker.cc. Be lazy in computing the name.

Change-Id: I1438efbda58369ddd0ac36eda8a5a0a6c6fdff77
diff --git a/runtime/mirror/class.h b/runtime/mirror/class.h
index 6a7faaa..d9094fc 100644
--- a/runtime/mirror/class.h
+++ b/runtime/mirror/class.h
@@ -1147,11 +1147,11 @@
 
   // The following data exist in real class objects.
   // Embedded Imtable, for class object that's not an interface, fixed size.
-  ImTableEntry embedded_imtable_[0];
+  // ImTableEntry embedded_imtable_[0];
   // Embedded Vtable, for class object that's not an interface, variable size.
-  VTableEntry embedded_vtable_[0];
+  // VTableEntry embedded_vtable_[0];
   // Static fields, variable size.
-  uint32_t fields_[0];
+  // uint32_t fields_[0];
 
   // java.lang.Class
   static GcRoot<Class> java_lang_Class_;