Remember and reuse derived map for external arrays

src/bootstrapper.cc

 // Copyright 2006-2008 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 1918 matching lines @@
           ASSERT(!to->HasFastProperties());
           // Add to dictionary.
           Handle<String> key = Handle<String>(descs->GetKey(i));
           Handle<Object> callbacks(descs->GetCallbacksObject(i));
           PropertyDetails d =
               PropertyDetails(details.attributes(), CALLBACKS, details.index());
           SetNormalizedProperty(to, key, callbacks, d);
           break;
         }
         case MAP_TRANSITION:
+        case EXTERNAL_ARRAY_TRANSITION:
         case CONSTANT_TRANSITION:
         case NULL_DESCRIPTOR:
           // Ignore non-properties.
           break;
         case NORMAL:
           // Do not occur since the from object has fast properties.
         case INTERCEPTOR:
           // No element in instance descriptors have interceptor type.
           UNREACHABLE();
           break;
@@ skipping 143 matching lines @@
   return from + sizeof(NestingCounterType);
 }
 
 
 // Called when the top-level V8 mutex is destroyed.
 void Bootstrapper::FreeThreadResources() {
   ASSERT(!IsActive());
 }
 
 } }  // namespace v8::internal