Turn polymorphic stores monomorphic if store sequence matches.

src/property-details.h

Index: src/property-details.h
diff --git a/src/property-details.h b/src/property-details.h
index f025f152b7f02c46d641ba53f1b9f6a59d8336b0..f40c6d32af4609a1425c0ef482812dc1194f0829 100644
--- a/src/property-details.h
+++ b/src/property-details.h
@@ -103,6 +103,10 @@ class Representation {
     return kind_ == other.kind_;
   }
 
+  bool IsCompatibleForStore(const Representation& other) const {
+    return Equals(other);
+  }
+
   bool is_more_general_than(const Representation& other) const {
     ASSERT(kind_ != kExternal);
     ASSERT(other.kind_ != kExternal);