Add instrumentation to track down a crasher

src/objects.cc

 // Copyright 2013 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 <iomanip>
 #include <sstream>
 
 #include "src/accessors.h"
@@ skipping 4786 matching lines @@
   // Allocate the fixed array for the fields.
   Handle<FixedArray> fields = factory->NewFixedArray(
       number_of_allocated_fields);
 
   // Fill in the instance descriptor and the fields.
   int current_offset = 0;
   for (int i = 0; i < instance_descriptor_length; i++) {
     int index = Smi::cast(iteration_order->get(i))->value();
     Object* k = dictionary->KeyAt(index);
     DCHECK(dictionary->IsKey(k));
+    // Dictionary keys are internalized upon insertion.
+    // TODO(jkummerow): Turn this into a DCHECK if it's not hit in the wild.
+    CHECK(k->IsUniqueName());
+    Handle<Name> key(Name::cast(k), isolate);
 
     Object* value = dictionary->ValueAt(index);
-    Handle<Name> key;
-    if (k->IsSymbol()) {
-      key = handle(Symbol::cast(k));
-    } else {
-      // Ensure the key is a unique name before writing into the
-      // instance descriptor.
-      key = factory->InternalizeString(handle(String::cast(k)));
-    }
 
     PropertyDetails details = dictionary->DetailsAt(index);
     int enumeration_index = details.dictionary_index();
     PropertyType type = details.type();
 
     if (value->IsJSFunction()) {
       DataConstantDescriptor d(key, handle(value, isolate),
                                details.attributes());
       descriptors->Set(enumeration_index - 1, &d);
     } else if (type == DATA) {
@@ skipping 11337 matching lines @@
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 
 }  // namespace internal
 }  // namespace v8