Use dominance information for null optimization in write barrier.

Change-Id: I8b57dafcd321c9afa1bbfc6a0674cbea15cbf10c
diff --git a/compiler/optimizing/graph_visualizer.cc b/compiler/optimizing/graph_visualizer.cc
index d05c514..2c6c3b7 100644
--- a/compiler/optimizing/graph_visualizer.cc
+++ b/compiler/optimizing/graph_visualizer.cc
@@ -374,6 +374,11 @@
         << instance_of->MustDoNullCheck() << std::noboolalpha;
   }
 
+  void VisitArraySet(HArraySet* array_set) OVERRIDE {
+    StartAttributeStream("value_can_be_null") << std::boolalpha
+        << array_set->GetValueCanBeNull() << std::noboolalpha;
+  }
+
   void VisitInvoke(HInvoke* invoke) OVERRIDE {
     StartAttributeStream("dex_file_index") << invoke->GetDexMethodIndex();
     StartAttributeStream("method_name") << PrettyMethod(