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_method_info.h b/compiler/dex/mir_method_info.h
index a43238c..f927f1d 100644
--- a/compiler/dex/mir_method_info.h
+++ b/compiler/dex/mir_method_info.h
@@ -178,6 +178,8 @@
   uint16_t target_method_idx_;
   uint16_t vtable_idx_;
   int stats_flags_;
+
+  friend class ClassInitCheckEliminationTest;
 };
 
 }  // namespace art