Use Unique<Map> in HTransitionElementsKind.

src/x64/lithium-x64.h

Index: src/x64/lithium-x64.h
diff --git a/src/x64/lithium-x64.h b/src/x64/lithium-x64.h
index 136b2940a917a4d8b9efe266787b6a224800699f..9f45f97e25e7db72c5fd4572e9949b82ad43ccdc 100644
--- a/src/x64/lithium-x64.h
+++ b/src/x64/lithium-x64.h
@@ -2201,8 +2201,10 @@ class LTransitionElementsKind V8_FINAL : public LTemplateInstruction<0, 1, 2> {
 
   virtual void PrintDataTo(StringStream* stream) V8_OVERRIDE;
 
-  Handle<Map> original_map() { return hydrogen()->original_map(); }
-  Handle<Map> transitioned_map() { return hydrogen()->transitioned_map(); }
+  Handle<Map> original_map() { return hydrogen()->original_map().handle(); }
+  Handle<Map> transitioned_map() {
+    return hydrogen()->transitioned_map().handle();
+  }
   ElementsKind from_kind() { return hydrogen()->from_kind(); }
   ElementsKind to_kind() { return hydrogen()->to_kind(); }
 };