Reland parts of 'Use weak cells in map checks in polymorphic ICs'

src/objects-printer.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/disasm.h"
 #include "src/disassembler.h"
 #include "src/heap/objects-visiting.h"
 #include "src/jsregexp.h"
@@ skipping 829 matching lines @@
 }
 
 
 void PropertyCell::PropertyCellPrint(std::ostream& os) {  // NOLINT
   HeapObject::PrintHeader(os, "PropertyCell");
 }
 
 
 void WeakCell::WeakCellPrint(std::ostream& os) {  // NOLINT
   HeapObject::PrintHeader(os, "WeakCell");
+  if (cleared()) {
+    os << "\n - cleared";
+  } else {
+    os << "\n - value: " << Brief(value());
+  }
 }
 
 
 void Code::CodePrint(std::ostream& os) {  // NOLINT
   HeapObject::PrintHeader(os, "Code");
 #ifdef ENABLE_DISASSEMBLER
   if (FLAG_use_verbose_printer) {
     Disassemble(NULL, os);
   }
 #endif
@@ skipping 334 matching lines @@
       return SNPrintF(str, "#<%s>", s->PrivateSymbolToName());
     } else {
       return SNPrintF(str, "<%s>", String::cast(s->name())->ToCString().get());
     }
   }
 }
 
 
 #endif  // TRACE_MAPS
 } }  // namespace v8::internal