Class initialization check elimination.

Also, move null check elimination temporaries to the
ScopedArenaAllocator and reuse the same variables in the
class initialization check elimination.

Change-Id: Ic746f95427065506fa6016d4931e4cb8b34937af
diff --git a/compiler/dex/mir_field_info.h b/compiler/dex/mir_field_info.h
index e64e9fc..cad516d 100644
--- a/compiler/dex/mir_field_info.h
+++ b/compiler/dex/mir_field_info.h
@@ -203,6 +203,7 @@
   // -1 if the field is unresolved or there's no appropriate TypeId in that dex file.
   uint32_t storage_index_;
 
+  friend class ClassInitCheckEliminationTest;
   friend class LocalValueNumberingTest;
 };