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

src/runtime.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 10268 matching lines @@
           return maybe_value;
         }
         return value;
       } else {
         return heap->undefined_value();
       }
     }
     case INTERCEPTOR:
     case MAP_TRANSITION:
     case CONSTANT_TRANSITION:
-    case NULL_DESCRIPTOR:
       return heap->undefined_value();
     case HANDLER:
+    case NONEXISTENT:
       UNREACHABLE();
       return heap->undefined_value();
   }
   UNREACHABLE();  // keep the compiler happy
   return heap->undefined_value();
 }
 
 
 // Get debugger related details for an object property.
 // args[0]: object holding property
@@ skipping 3350 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal