Put making embedded maps in optimized code weak behind a flag.

src/lithium.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 411 matching lines @@
 
   if (generator.GenerateCode()) {
     if (FLAG_trace_codegen) {
       PrintF("Crankshaft Compiler - ");
     }
     CodeGenerator::MakeCodePrologue(info());
     Code::Flags flags = Code::ComputeFlags(kind);
     Handle<Code> code =
         CodeGenerator::MakeCodeEpilogue(&assembler, flags, info());
     generator.FinishCode(code);
-    RegisterDependentCodeForEmbeddedMaps(code);
+    if (FLAG_weak_embedded_maps_in_optimized_code) {
+      RegisterDependentCodeForEmbeddedMaps(code);
+    }
     CodeGenerator::PrintCode(code, info());
     return code;
   }
   return Handle<Code>::null();
 }
 
 
 void LChunk::RegisterDependentCodeForEmbeddedMaps(Handle<Code> code) {
   ZoneList<Handle<Map> > maps(1, zone());
   int mode_mask = RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT);
   for (RelocIterator it(*code, mode_mask); !it.done(); it.next()) {
     RelocInfo::Mode mode = it.rinfo()->rmode();
     if (mode == RelocInfo::EMBEDDED_OBJECT &&
         it.rinfo()->target_object()->IsMap()) {
       Handle<Map> map(Map::cast(it.rinfo()->target_object()));
       if (map->CanTransition()) {
         maps.Add(map, zone());
       }
     }
   }
   for (int i = 0; i < maps.length(); i++) {
     maps.at(i)->AddDependentCode(code);
   }
 }
 
 } }  // namespace v8::internal