Use UniqueSet<T> and Unique<T> in HCheckMaps and HCheckValue.

src/hydrogen-escape-analysis.cc

Index: src/hydrogen-escape-analysis.cc
diff --git a/src/hydrogen-escape-analysis.cc b/src/hydrogen-escape-analysis.cc
index 997e4f9445f79ab3f7ba079acb54be1f6e25deb8..3a7e10dbe427f178604c950bf9ca92e6b162c2d0 100644
--- a/src/hydrogen-escape-analysis.cc
+++ b/src/hydrogen-escape-analysis.cc
@@ -154,9 +154,8 @@ HValue* HEscapeAnalysisPhase::NewMapCheckAndInsert(HCapturedObject* state,
   HValue* value = state->map_value();
   // TODO(mstarzinger): This will narrow a map check against a set of maps
   // down to the first element in the set. Revisit and fix this.
-  Handle<Map> map_object = mapcheck->map_set()->first();
-  UniqueValueId map_id = mapcheck->map_unique_ids()->first();
-  HCheckValue* check = HCheckValue::New(zone, NULL, value, map_object, map_id);
+  HCheckValue* check = HCheckValue::New(
+      zone, NULL, value, mapcheck->first_map(), false);
   check->InsertBefore(mapcheck);
   return check;
 }