Add flag to control background finalization.

runtime/vm/flag_list.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_FLAG_LIST_H_
 #define VM_FLAG_LIST_H_
 
 // Don't use USING_DBC outside of this file.
 #if defined(TARGET_ARCH_DBC)
 #define USING_DBC true
@@ skipping 23 matching lines @@
 //   R(name, product_value, type, default_value, comment)
 //   D(name, type, default_value, comment)
 //   C(name, precompiled_value, product_value, type, default_value, comment)
 #define FLAG_LIST(P, R, D, C)                                                  \
 P(always_megamorphic_calls, bool, false,                                       \
   "Instance call always as megamorphic.")                                      \
 P(background_compilation, bool, USING_MULTICORE,                               \
   "Run optimizing compilation in background")                                  \
 R(background_compilation_stop_alot, false, bool, false,                        \
   "Stress test system: stop background compiler often.")                       \
+P(background_finalization, bool, USING_MULTICORE,                              \
+  "Run weak handle finalizers in background")                                  \
 R(break_at_isolate_spawn, false, bool, false,                                  \
   "Insert a one-time breakpoint at the entrypoint for all spawned isolates")   \
 C(collect_code, false, true, bool, true,                                       \
   "Attempt to GC infrequently used code.")                                     \
 P(collect_dynamic_function_names, bool, true,                                  \
   "Collects all dynamic function names to identify unique targets")            \
 R(concurrent_sweep, USING_MULTICORE, bool, USING_MULTICORE,                    \
   "Concurrent sweep for old generation.")                                      \
 R(dedup_instructions, true, bool, false,                                       \
   "Canonicalize instructions when precompiling.")                              \
@@ skipping 141 matching lines @@
 P(verbose_gc_hdr, int, 40,                                                     \
   "Print verbose GC header interval.")                                         \
 R(verify_after_gc, false, bool, false,                                         \
   "Enables heap verification after GC.")                                       \
 R(verify_before_gc, false, bool, false,                                        \
   "Enables heap verification before GC.")                                      \
 D(verify_on_transition, bool, false,                                           \
   "Verify on dart <==> VM.")                                                   \
 
 #endif  // VM_FLAG_LIST_H_