Remember and reuse derived map for external arrays

src/runtime.cc

 // Copyright 2010 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 9290 matching lines @@
           }
           return maybe_value;
         }
         return value;
       } else {
         return heap->undefined_value();
       }
     }
     case INTERCEPTOR:
     case MAP_TRANSITION:
+    case EXTERNAL_ARRAY_TRANSITION:
     case CONSTANT_TRANSITION:
     case NULL_DESCRIPTOR:
       return heap->undefined_value();
     default:
       UNREACHABLE();
   }
   UNREACHABLE();
   return heap->undefined_value();
 }
 
@@ skipping 2904 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     COUNTERS->gc_last_resort_from_js()->Increment();
     HEAP->CollectAllGarbage(false);
   }
 }
 
 
 } }  // namespace v8::internal