Various cleanups in check elimination.

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 14e8bbf80f02e2d925cde28ec5706b61f43aec82..8514d889f05a0054791bfdfc08263d9573ef3056 100644
--- a/src/hydrogen-escape-analysis.cc
+++ b/src/hydrogen-escape-analysis.cc
@@ -132,7 +132,7 @@ HValue* HEscapeAnalysisPhase::NewMapCheckAndInsert(HCapturedObject* state,
   // 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.
   HCheckValue* check = HCheckValue::New(
-      zone, NULL, value, mapcheck->first_map(), false);
+      zone, NULL, value, mapcheck->maps()->at(0), false);
   check->InsertBefore(mapcheck);
   return check;
 }