[debugging] Show internal fields with %DebugPrint

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/objects.h"
 
 #include <memory>
 
 #include "src/disasm.h"
 #include "src/disassembler.h"
@@ skipping 401 matching lines @@
     os << "DictionaryProperties";
   }
   PrototypeIterator iter(obj->GetIsolate(), obj);
   os << "]\n - prototype = " << reinterpret_cast<void*>(iter.GetCurrent());
   os << "\n - elements = " << Brief(obj->elements()) << " ["
      << ElementsKindToString(obj->map()->elements_kind());
   if (obj->elements()->map() == obj->GetHeap()->fixed_cow_array_map()) {
     os << " (COW)";
   }
   os << "]";
+  if (obj->GetInternalFieldCount() > 0) {
+    os << "\n - internal fields: " << obj->GetInternalFieldCount();
+  }
 }
 
 
 static void JSObjectPrintBody(std::ostream& os, JSObject* obj,  // NOLINT
                               bool print_elements = true) {
   os << "\n - properties = {";
   obj->PrintProperties(os);
   os << "\n }\n";
   if (print_elements && obj->elements()->length() > 0) {
     os << " - elements = {";
     obj->PrintElements(os);
     os << "\n }\n";
   }
+  int internal_fields = obj->GetInternalFieldCount();
+  if (internal_fields > 0) {
+    os << " - internal fields = {";
+    for (int i = 0; i < internal_fields; i++) {
+      os << "\n    " << Brief(obj->GetInternalField(i));
+    }
+    os << "\n }\n";
+  }
 }
 
 
 void JSObject::JSObjectPrint(std::ostream& os) {  // NOLINT
   JSObjectPrintHeader(os, this, nullptr);
   JSObjectPrintBody(os, this);
 }
 
 void JSArray::JSArrayPrint(std::ostream& os) {  // NOLINT
   JSObjectPrintHeader(os, this, "JSArray");
@@ skipping 977 matching lines @@
 void JSObject::PrintTransitions(std::ostream& os) {  // NOLINT
   Object* transitions = map()->raw_transitions();
   int num_transitions = TransitionArray::NumberOfTransitions(transitions);
   if (num_transitions == 0) return;
   os << "\n - transitions";
   TransitionArray::PrintTransitions(os, transitions, false);
 }
 #endif  // defined(DEBUG) || defined(OBJECT_PRINT)
 }  // namespace internal
 }  // namespace v8