Oilpan: remove too strong start-of-heap-object assert.

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 846 matching lines @@
     // to be not reachable during the marking phase, but it has yet to be swept
     // and finalized. The predicate returns false in all other cases.
     //
     // Holding a reference to an already-dead object is not a valid state
     // to be in; willObjectBeLazilySwept() has undefined behavior if passed
     // such a reference.
     template<typename T>
     static bool willObjectBeLazilySwept(const T* objectPointer)
     {
         static_assert(IsGarbageCollectedType<T>::value, "only objects deriving from GarbageCollected can be used.");
-#if ENABLE(ASSERT)
-        ASSERT(objectPointer);
-        HeapObjectHeader::fromPayload(objectPointer)->checkHeader();
-#endif
 #if ENABLE(OILPAN)
         BaseHeapPage* page = pageFromObject(objectPointer);
         if (page->hasBeenSwept())
             return false;
         ASSERT(page->heap()->threadState()->isSweepingInProgress());
 
         return !ObjectAliveTrait<T>::isHeapObjectAlive(s_markingVisitor, const_cast<T*>(objectPointer));
 #else
         // FIXME: remove when lazy sweeping is always on
         // (cf. ThreadState::postGCProcessing()).
@@ skipping 1551 matching lines @@
 template<typename T, size_t inlineCapacity>
 struct GCInfoTrait<HeapVector<T, inlineCapacity>> : public GCInfoTrait<Vector<T, inlineCapacity, HeapAllocator>> { };
 template<typename T, size_t inlineCapacity>
 struct GCInfoTrait<HeapDeque<T, inlineCapacity>> : public GCInfoTrait<Deque<T, inlineCapacity, HeapAllocator>> { };
 template<typename T, typename U, typename V>
 struct GCInfoTrait<HeapHashCountedSet<T, U, V>> : public GCInfoTrait<HashCountedSet<T, U, V, HeapAllocator>> { };
 
 } // namespace blink
 
 #endif // Heap_h