[heap] Implement concurrent marking boilerplate.

src/heap/heap.h

 // Copyright 2012 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.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 300 matching lines @@
   V(InfinityValue)                      \
   V(MinusZeroValue)                     \
   V(MinusInfinityValue)                 \
   V(EmptyWeakCell)                      \
   V(empty_string)                       \
   PRIVATE_SYMBOL_LIST(V)
 
 // Forward declarations.
 class AllocationObserver;
 class ArrayBufferTracker;
+class ConcurrentMarking;
 class GCIdleTimeAction;
 class GCIdleTimeHandler;
 class GCIdleTimeHeapState;
 class GCTracer;
 class HeapObjectsFilter;
 class HeapStats;
 class HistogramTimer;
 class Isolate;
 class LocalEmbedderHeapTracer;
 class MemoryAllocator;
@@ skipping 1952 matching lines @@
 
   Scavenger* scavenge_collector_;
 
   MarkCompactCollector* mark_compact_collector_;
 
   MemoryAllocator* memory_allocator_;
 
   StoreBuffer* store_buffer_;
 
   IncrementalMarking* incremental_marking_;
+  ConcurrentMarking* concurrent_marking_;
 
   GCIdleTimeHandler* gc_idle_time_handler_;
 
   MemoryReducer* memory_reducer_;
 
   ObjectStats* live_object_stats_;
   ObjectStats* dead_object_stats_;
 
   ScavengeJob* scavenge_job_;
 
@@ skipping 63 matching lines @@
   bool fast_promotion_mode_;
 
   // Used for testing purposes.
   bool force_oom_;
   bool delay_sweeper_tasks_for_testing_;
 
   HeapObject* pending_layout_change_object_;
 
   // Classes in "heap" can be friends.
   friend class AlwaysAllocateScope;
+  friend class ConcurrentMarking;
   friend class GCCallbacksScope;
   friend class GCTracer;
   friend class HeapIterator;
   friend class IdleScavengeObserver;
   friend class IncrementalMarking;
   friend class IncrementalMarkingJob;
   friend class LargeObjectSpace;
   friend class MarkCompactCollector;
   friend class MarkCompactMarkingVisitor;
   friend class NewSpace;
@@ skipping 230 matching lines @@
   friend class LargeObjectSpace;
   friend class NewSpace;
   friend class PagedSpace;
   DISALLOW_COPY_AND_ASSIGN(AllocationObserver);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_