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

test/cctest/heap/heap-utils.h

Index: test/cctest/heap/heap-utils.h
diff --git a/test/cctest/heap/heap-utils.h b/test/cctest/heap/heap-utils.h
index e03e6fa6e0461df12f6ec8a204a9975b782d09c8..753af11b1dcd2bbe5831f0765e300cc4c8d0393d 100644
--- a/test/cctest/heap/heap-utils.h
+++ b/test/cctest/heap/heap-utils.h
@@ -15,6 +15,12 @@ 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);