Enable per thread heap for database thread

third_party/WebKit/Source/platform/heap/Heap.h

 /*
  * Copyright (C) 2013 Google Inc. 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
@@ skipping 184 matching lines @@
     static inline bool isHeapObjectAlive(T* object)
     {
         static_assert(sizeof(T), "T must be fully defined");
         // The strongification of collections relies on the fact that once a
         // collection has been strongified, there is no way that it can contain
         // non-live entries, so no entries will be removed. Since you can't set
         // the mark bit on a null pointer, that means that null pointers are
         // always 'alive'.
         if (!object)
             return true;
+        // TODO(keishi): some tests create CrossThreadPersistent on non attached threads.

[haraken, 2016/05/24 16:15:28]

Do you know what tests are doing that?

But conceptually, I think it is valid to create a CrossThreadPersistent on a
non-attached thread.

+        DCHECK(!ThreadState::current() || &ThreadState::current()->heap() == &pageFromObject(object)->arena()->getThreadState()->heap());
         return ObjectAliveTrait<T>::isHeapObjectAlive(object);
     }
     template<typename T>
     static inline bool isHeapObjectAlive(const Member<T>& member)
     {
         return isHeapObjectAlive(member.get());
     }
     template<typename T>
     static inline bool isHeapObjectAlive(const WeakMember<T>& member)
     {
@@ skipping 379 matching lines @@
 void VisitorHelper<Derived>::handleWeakCell(Visitor* self, void* object)
 {
     T** cell = reinterpret_cast<T**>(object);
     if (*cell && !ObjectAliveTrait<T>::isHeapObjectAlive(*cell))
         *cell = nullptr;
 }
 
 } // namespace blink
 
 #endif // Heap_h