Use just one marking deque.

src/heap/mark-compact.h

Index: src/heap/mark-compact.h
diff --git a/src/heap/mark-compact.h b/src/heap/mark-compact.h
index b1ad5b8a80ee6547e9a03708a473a46c913822ce..089aca3dcda9ded6a472d06ea64dc39ef5abdeff 100644
--- a/src/heap/mark-compact.h
+++ b/src/heap/mark-compact.h
@@ -517,9 +517,9 @@ class MarkCompactCollector {
   // Performs a global garbage collection.
   void CollectGarbage();
 
-  enum CompactionMode { INCREMENTAL_COMPACTION, NON_INCREMENTAL_COMPACTION };
+  enum MarkingMode { INCREMENTAL, NON_INCREMENTAL };
 
-  bool StartCompaction(CompactionMode mode);
+  bool StartCompaction(MarkingMode mode);
 
   void AbortCompaction();
 
@@ -771,12 +771,6 @@ class MarkCompactCollector {
   // otherwise a map can die and deoptimize the code.
   void ProcessTopOptimizedFrame(ObjectVisitor* visitor);
 
-  // Mark objects reachable (transitively) from objects in the marking
-  // stack.  This function empties the marking stack, but may leave
-  // overflowed objects in the heap, in which case the marking stack's
-  // overflow flag will be set.
-  void EmptyMarkingDeque();
-
   // Refill the marking stack with overflowed objects from the heap.  This
   // function either leaves the marking stack full or clears the overflow
   // flag on the marking stack.
@@ -866,6 +860,21 @@ class MarkCompactCollector {
   // Updates store buffer and slot buffer for a pointer in a migrating object.
   void RecordMigratedSlot(Object* value, Address slot);
 
+  MarkingDeque* marking_deque() { return &marking_deque_; }
+
+  void EnsureMarkingDequeIsCommittedAndInitialize();
+
+  void InitializeMarkingDeque();
+
+  void UncommitMarkingDeque();
+
+  // Mark objects reachable (transitively) from objects in the marking
+  // stack.  This function empties the marking stack, but may leave
+  // overflowed objects in the heap, in which case the marking stack's
+  // overflow flag will be set.
+  template <MarkingMode mode>
+  void EmptyMarkingDeque();
+
 #ifdef DEBUG
   friend class MarkObjectVisitor;
   static void VisitObject(HeapObject* obj);
@@ -875,6 +884,8 @@ class MarkCompactCollector {
 #endif
 
   Heap* heap_;
+  base::VirtualMemory* marking_deque_memory_;
+  bool marking_deque_memory_committed_;
   MarkingDeque marking_deque_;
   CodeFlusher* code_flusher_;
   bool have_code_to_deoptimize_;
@@ -885,6 +896,8 @@ class MarkCompactCollector {
   SmartPointer<FreeList> free_list_old_data_space_;
   SmartPointer<FreeList> free_list_old_pointer_space_;
 
+  friend class IncrementalMarking;
+  friend class IncrementalMarkingMarkingVisitor;
   friend class Heap;
 };