Ensure object ArraySet with null value does not need a type check.

The art::PrepareForRegisterAllocation visitor can remove an
art::BoundType instruction as value input of an
art::ArraySet instruction, possibly replacing it with an
art::NullConstant.  If this happens, remove the need for a
type check in this art::ArraySet.

Bug: 27638110
Change-Id: I6270f8a8e22822a24d8a5919df427ca9c64d121b
diff --git a/compiler/optimizing/graph_visualizer.cc b/compiler/optimizing/graph_visualizer.cc
index 4f1e90c..3a9d242 100644
--- a/compiler/optimizing/graph_visualizer.cc
+++ b/compiler/optimizing/graph_visualizer.cc
@@ -382,6 +382,8 @@
   void VisitArraySet(HArraySet* array_set) OVERRIDE {
     StartAttributeStream("value_can_be_null") << std::boolalpha
         << array_set->GetValueCanBeNull() << std::noboolalpha;
+    StartAttributeStream("needs_type_check") << std::boolalpha
+        << array_set->NeedsTypeCheck() << std::noboolalpha;
   }
 
   void VisitCompare(HCompare* compare) OVERRIDE {