In-place shrinking of descriptor arrays with non-live transitions.

src/property.cc

Index: src/property.cc
diff --git a/src/property.cc b/src/property.cc
index 8c69541be5c348c695df94e214c38f657e9a7458..3258b8cb3a7ca4363561aca43671d58acd29c63f 100644
--- a/src/property.cc
+++ b/src/property.cc
@@ -89,8 +89,8 @@ void LookupResult::Print(FILE* out) {
       GetTransitionMap()->Print(out);
       PrintF(out, "\n");
       break;
-    case NULL_DESCRIPTOR:
-      PrintF(out, " =type = null descriptor\n");
+    case NONEXISTENT:
+      UNREACHABLE();
       break;
   }
 }
@@ -123,8 +123,10 @@ bool Descriptor::ContainsTransition() {
     case CONSTANT_FUNCTION:
     case HANDLER:
     case INTERCEPTOR:
-    case NULL_DESCRIPTOR:
       return false;
+    case NONEXISTENT:
+      UNREACHABLE();
+      break;
   }
   UNREACHABLE();  // Keep the compiler happy.
   return false;