Refactoring only: Make the handling of PropertyType more explicit.

src/property.h

Index: src/property.h
diff --git a/src/property.h b/src/property.h
index ffea41e66688ae46af057dc51736f0bad54384c1..133abc1b42ef0bd50e307485f5e0f7cc3fb7a300 100644
--- a/src/property.h
+++ b/src/property.h
@@ -292,10 +292,10 @@ class LookupResult BASE_EMBEDDED {
     }
   }
 
+
   Map* GetTransitionMap() {
     ASSERT(lookup_type_ == DESCRIPTOR_TYPE);
-    ASSERT(type() == MAP_TRANSITION || type() == CONSTANT_TRANSITION ||
-           type() == ELEMENTS_TRANSITION);
+    ASSERT(IsTransitionType(type()));
     return Map::cast(GetValue());
   }