[heap] Implement simple concurrent marking deque.

test/unittests/BUILD.gn

 # Copyright 2016 The V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("../../gni/v8.gni")
 
 v8_executable("unittests") {
   testonly = true
 
   sources = [
@@ skipping 82 matching lines @@
     "compiler/state-values-utils-unittest.cc",
     "compiler/tail-call-optimization-unittest.cc",
     "compiler/typed-optimization-unittest.cc",
     "compiler/typer-unittest.cc",
     "compiler/value-numbering-reducer-unittest.cc",
     "compiler/zone-stats-unittest.cc",
     "counters-unittest.cc",
     "eh-frame-iterator-unittest.cc",
     "eh-frame-writer-unittest.cc",
     "heap/bitmap-unittest.cc",
+    "heap/concurrent-marking-deque-unittest.cc",
     "heap/embedder-tracing-unittest.cc",
     "heap/gc-idle-time-handler-unittest.cc",
     "heap/gc-tracer-unittest.cc",
     "heap/heap-unittest.cc",
     "heap/marking-unittest.cc",
     "heap/memory-reducer-unittest.cc",
     "heap/scavenge-job-unittest.cc",
     "heap/slot-set-unittest.cc",
     "heap/spaces-unittest.cc",
     "heap/unmapper-unittest.cc",
@@ skipping 97 matching lines @@
     deps += [ "../..:v8" ]
   }
 
   if (is_win) {
     # This warning is benignly triggered by the U16 and U32 macros in
     # bytecode-utils.h.
     # C4309: 'static_cast': truncation of constant value
     cflags = [ "/wd4309" ]
   }
 }