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

src/ast.cc

Index: src/ast.cc
diff --git a/src/ast.cc b/src/ast.cc
index b790e2536da6acc8b89f4b3ee4920c86ea046244..fb9db7cda209199fca38da5c3205e009fdd10780 100644
--- a/src/ast.cc
+++ b/src/ast.cc
@@ -520,9 +520,11 @@ bool Call::ComputeTarget(Handle<Map> type, Handle<String> name) {
           return false;
         case MAP_TRANSITION:
         case CONSTANT_TRANSITION:
-        case NULL_DESCRIPTOR:
           // Perhaps something interesting is up in the prototype chain...
           break;
+        case NONEXISTENT:
+          UNREACHABLE();
+          break;
       }
     }
     // If we reach the end of the prototype chain, we don't know the target.