[heap,snapshot] Replace first page size from snapshots with page trimming

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 {
 namespace internal {
 namespace heap {
 
 void SealCurrentObjects(Heap* heap);
 
 int FixedArrayLenFromSize(int size);
 
+// Fill a page with fixed arrays leaving remainder behind. The function does
+// not create additional fillers and assumes that the space has just been
+// sealed.
+std::vector<Handle<FixedArray>> FillOldSpacePageWithFixedArrays(Heap* heap,
+                                                                int remainder);
+
 std::vector<Handle<FixedArray>> CreatePadding(
     Heap* heap, int padding_size, PretenureFlag tenure,
     int object_size = Page::kMaxRegularHeapObjectSize);
 
 void AllocateAllButNBytes(
     v8::internal::NewSpace* space, int extra_bytes,
     std::vector<Handle<FixedArray>>* out_handles = nullptr);
 
 void FillCurrentPage(v8::internal::NewSpace* space,
                      std::vector<Handle<FixedArray>>* out_handles = nullptr);
@@ skipping 14 matching lines @@
 
 void AbandonCurrentlyFreeMemory(PagedSpace* space);
 
 void GcAndSweep(Heap* heap, AllocationSpace space);
 
 }  // namespace heap
 }  // namespace internal
 }  // namespace v8
 
 #endif  // HEAP_HEAP_UTILS_H_