[turbofan] Port Crankshaft's weak objects mechanism to TurboFan.

src/objects-inl.h

 // 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.
 //
 // Review notes:
 //
 // - The use of macros in these inline functions may seem superfluous
 // but it is absolutely needed to make sure gcc generates optimal
 // code. gcc is not happy when attempting to inline too deep.
 //
@@ skipping 5220 matching lines @@
 }
 
 
 Object* Code::GetObjectFromEntryAddress(Address location_of_address) {
   return HeapObject::
       FromAddress(Memory::Address_at(location_of_address) - Code::kHeaderSize);
 }
 
 
 bool Code::CanContainWeakObjects() {
-  // is_turbofanned() implies !can_have_weak_objects().
-  DCHECK(!is_optimized_code() || !is_turbofanned() || !can_have_weak_objects());
   return is_optimized_code() && can_have_weak_objects();
 }
 
 
 bool Code::IsWeakObject(Object* object) {
   return (CanContainWeakObjects() && IsWeakObjectInOptimizedCode(object));
 }
 
 
 bool Code::IsWeakObjectInOptimizedCode(Object* object) {
@@ skipping 2547 matching lines @@
 #undef WRITE_INT64_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 #undef NOBARRIER_READ_BYTE_FIELD
 #undef NOBARRIER_WRITE_BYTE_FIELD
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_OBJECTS_INL_H_