fixup! src: fix timing of snapshot serialize callback

Author: joyeecheung

test/parallel/test-buffer-alloc-unsafe-is-initialized-with-zero-fill-flag.js

@@ -0,0 +1,17 @@
+// Flags: --expose-internals --zero-fill-buffers
+// Verifies that Buffer.allocUnsafe() allocates initialized memory under --zero-fill-buffers by
+// checking the usage count of the relevant native allocator code path.
+'use strict';
+
+const common = require('../common');
+if (!common.isDebug) {
+  common.skip('Only works in debug mode');
+}
+const { internalBinding } = require('internal/test/binding');
+const { getGenericUsageCount } = internalBinding('debug');
+const assert = require('assert');
+
+const initialCount = getGenericUsageCount('NodeArrayBufferAllocator.Allocate.ZeroFilled');
+Buffer.allocUnsafe(Buffer.poolSize + 1);
+const newCount = getGenericUsageCount('NodeArrayBufferAllocator.Allocate.ZeroFilled');
+assert.notStrictEqual(newCount, initialCount);