Enable deferred free for syzyasan builds behind a feature.

chrome/common/chrome_features.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/common/chrome_features.h"
 
 namespace features {
 
 // All features in alphabetical order.
 
@@ skipping 30 matching lines @@
     "ViewsSimplifiedFullscreenUI",
 #if defined(USE_AURA)
     // Windows, Linux, Chrome OS.
     base::FEATURE_ENABLED_BY_DEFAULT,
 #else
     // Mac, Android.
     base::FEATURE_DISABLED_BY_DEFAULT,
 #endif
 };
 
+#if defined(SYZYASAN)
+// Enable the deferred free mechanism in the syzyasan module, which helps the
+// performance by deferring some work on the critical path to a background
+// thread.
+const base::Feature kSyzyasanDeferredFree{"SyzyasanDeferredFree",
+                                          base::FEATURE_DISABLED_BY_DEFAULT};
+#endif
+
 }  // namespace features