To diagnose chromium bug 284577, some additional CHECKS. TODOs are

src/objects-debug.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 310 matching lines @@
         Representation r = descriptors->GetDetails(i).representation();
         int field = descriptors->GetFieldIndex(i);
         Object* value = RawFastPropertyAt(field);
         if (r.IsDouble()) ASSERT(value->IsHeapNumber());
         if (value->IsUninitialized()) continue;
         if (r.IsSmi()) ASSERT(value->IsSmi());
         if (r.IsHeapObject()) ASSERT(value->IsHeapObject());
       }
     }
   }
-  CHECK_EQ((map()->has_fast_smi_or_object_elements() ||
-             (elements() == GetHeap()->empty_fixed_array())),
-            (elements()->map() == GetHeap()->fixed_array_map() ||
-             elements()->map() == GetHeap()->fixed_cow_array_map()));
-  CHECK(map()->has_fast_object_elements() == HasFastObjectElements());
+
+  // TODO(hpayer): deal gracefully with partially constructed JSObjects, when
+  // allocation folding is turned off.
+  if (reinterpret_cast<Map*>(elements()) !=
+      GetHeap()->one_pointer_filler_map()) {
+    CHECK_EQ((map()->has_fast_smi_or_object_elements() ||
+              (elements() == GetHeap()->empty_fixed_array())),
+             (elements()->map() == GetHeap()->fixed_array_map() ||
+              elements()->map() == GetHeap()->fixed_cow_array_map()));
+    CHECK(map()->has_fast_object_elements() == HasFastObjectElements());
+  }
 }
 
 
 void Map::MapVerify() {
   CHECK(!HEAP->InNewSpace(this));
   CHECK(FIRST_TYPE <= instance_type() && instance_type() <= LAST_TYPE);
   CHECK(instance_size() == kVariableSizeSentinel ||
          (kPointerSize <= instance_size() &&
           instance_size() < HEAP->Capacity()));
   VerifyHeapPointer(prototype());
@@ skipping 322 matching lines @@
             DependentCode::kWeaklyEmbeddedGroup, this));
       }
     }
   }
 }
 
 
 void JSArray::JSArrayVerify() {
   JSObjectVerify();
   CHECK(length()->IsNumber() || length()->IsUndefined());
-  CHECK(elements()->IsUndefined() ||
-         elements()->IsFixedArray() ||
-         elements()->IsFixedDoubleArray());
+  // TODO(hpayer): deal gracefully with partially constructed JSObjects, when
+  // allocation folding is turned off.
+  if (reinterpret_cast<Map*>(elements()) !=
+      GetHeap()->one_pointer_filler_map()) {
+    CHECK(elements()->IsUndefined() ||
+          elements()->IsFixedArray() ||
+          elements()->IsFixedDoubleArray());
+    // TODO(mvstanton): to diagnose chromium bug 284577, remove after.
+    AllocationMemento* memento = AllocationMemento::FindForJSObject(this);
+    if (memento != NULL && memento->IsValid()) {
+      memento->AllocationMementoVerify();
+    }
+  }
 }
 
 
 void JSSet::JSSetVerify() {
   CHECK(IsJSSet());
   JSObjectVerify();
   VerifyHeapPointer(table());
   CHECK(table()->IsHashTable() || table()->IsUndefined());
 }
 
@@ skipping 478 matching lines @@
   for (int i = 0; i < number_of_transitions(); ++i) {
     if (!CheckOneBackPointer(current_map, GetTarget(i))) return false;
   }
   return true;
 }
 
 
 #endif  // DEBUG
 
 } }  // namespace v8::internal