Enable deferred free for syzyasan builds behind a feature.

chrome/common/chrome_features.cc

Index: chrome/common/chrome_features.cc
diff --git a/chrome/common/chrome_features.cc b/chrome/common/chrome_features.cc
index a7643b349ff316fe7b55bfac6309d4c55f813212..e1c558bcde2c91b16cc46409eb3732333673bb01 100644
--- a/chrome/common/chrome_features.cc
+++ b/chrome/common/chrome_features.cc
@@ -48,4 +48,12 @@ const base::Feature kSimplifiedFullscreenUI{
 #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