Provide a tagged allocation top pointer.

test/cctest/heap/heap-utils.h

 // Copyright 2016 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 HEAP_HEAP_UTILS_H_
 #define HEAP_HEAP_UTILS_H_
 
 #include "src/heap/heap.h"
 
 namespace v8 {
@@ skipping 26 matching lines @@
 // marking is completed.
 void SimulateIncrementalMarking(i::Heap* heap, bool force_completion = true);
 
 // Helper function that simulates a full old-space in the heap.
 void SimulateFullSpace(v8::internal::PagedSpace* space);
 
 void AbandonCurrentlyFreeMemory(PagedSpace* space);
 
 void GcAndSweep(Heap* heap, AllocationSpace space);
 
+// Helper function to make sure that the new space's top is not double-aligned.
+void MakeSureNewSpaceTopIsNotDoubleAligned(i::Heap* heap);
+
 }  // namespace heap
 }  // namespace internal
 }  // namespace v8
 
 #endif  // HEAP_HEAP_UTILS_H_