Fix symbol printing in migration / generalization tracing

src/objects.cc

 // Copyright 2013 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 1558 matching lines @@
                               const char* reason,
                               int modify_index,
                               int split,
                               int descriptors,
                               bool constant_to_field,
                               Representation old_representation,
                               Representation new_representation) {
   PrintF(file, "[generalizing ");
   constructor_name()->PrintOn(file);
   PrintF(file, "] ");
-  String::cast(instance_descriptors()->GetKey(modify_index))->PrintOn(file);
+  Name* name = instance_descriptors()->GetKey(modify_index);
+  if (name->IsString()) {
+    String::cast(name)->PrintOn(file);
+  } else {
+    PrintF(file, "{symbol %p}", static_cast<void*>(name));
+  }
   if (constant_to_field) {
     PrintF(file, ":c->f");
   } else {
     PrintF(file, ":%s->%s",
            old_representation.Mnemonic(),
            new_representation.Mnemonic());
   }
   PrintF(file, " (");
   if (strlen(reason) > 0) {
     PrintF(file, "%s", reason);
@@ skipping 19 matching lines @@
     Representation n_r = n->GetDetails(i).representation();
     if (!o_r.Equals(n_r)) {
       String::cast(o->GetKey(i))->PrintOn(file);
       PrintF(file, ":%s->%s ", o_r.Mnemonic(), n_r.Mnemonic());
     } else if (o->GetDetails(i).type() == CONSTANT &&
                n->GetDetails(i).type() == FIELD) {
       Name* name = o->GetKey(i);
       if (name->IsString()) {
         String::cast(name)->PrintOn(file);
       } else {
-        PrintF(file, "???");
+        PrintF(file, "{symbol %p}", static_cast<void*>(name));
       }
       PrintF(file, " ");
     }
   }
   PrintF(file, "\n");
 }
 
 
 void HeapObject::HeapObjectShortPrint(StringStream* accumulator) {
   Heap* heap = GetHeap();
@@ skipping 14862 matching lines @@
 #define ERROR_MESSAGES_TEXTS(C, T) T,
   static const char* error_messages_[] = {
       ERROR_MESSAGES_LIST(ERROR_MESSAGES_TEXTS)
   };
 #undef ERROR_MESSAGES_TEXTS
   return error_messages_[reason];
 }
 
 
 } }  // namespace v8::internal