[snapshot] introduce SnapshotCreator API.

src/heap/heap.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.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 825 matching lines @@
 
   bool DeoptMaybeTenuredAllocationSites() {
     return new_space_.IsAtMaximumCapacity() && maximum_size_scavenges_ == 0;
   }
 
   void AddWeakObjectToCodeDependency(Handle<HeapObject> obj,
                                      Handle<DependentCode> dep);
 
   DependentCode* LookupWeakObjectToCodeDependency(Handle<HeapObject> obj);
 
+  void CompactWeakFixedArrays();
+
   void AddRetainedMap(Handle<Map> map);
 
   // This event is triggered after successful allocation of a new object made
   // by runtime. Allocations of target space for object evacuation do not
   // trigger the event. In order to track ALL allocations one must turn off
   // FLAG_inline_new and FLAG_use_allocation_folding.
   inline void OnAllocationEvent(HeapObject* object, int size_in_bytes);
 
   // This event is triggered after object is moved to a new place.
   inline void OnMoveEvent(HeapObject* target, HeapObject* source,
@@ skipping 1812 matching lines @@
   friend class LargeObjectSpace;
   friend class NewSpace;
   friend class PagedSpace;
   DISALLOW_COPY_AND_ASSIGN(AllocationObserver);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_