Use just one marking deque.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index b1738ee7256beb292c6f702fe69977ae1bde25f1..389edcd961c9f8ada4dbe7bbc468ae68285daccd 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -768,7 +768,6 @@ void Heap::CollectAllAvailableGarbage(const char* gc_reason) {
   mark_compact_collector()->SetFlags(kNoGCFlags);
   new_space_.Shrink();
   UncommitFromSpace();
-  incremental_marking()->UncommitMarkingDeque();
 }
 
 
@@ -1133,6 +1132,9 @@ bool Heap::PerformGarbageCollection(
         amount_of_external_allocated_memory_;
     old_generation_allocation_limit_ = OldGenerationAllocationLimit(
         PromotedSpaceSizeOfObjects(), freed_global_handles);
+    // We finished a marking cycle. We can uncommit the marking deque until
+    // we start marking again.
+    mark_compact_collector_.UncommitMarkingDeque();
   }
 
   {
@@ -4410,7 +4412,7 @@ void Heap::TryFinalizeIdleIncrementalMarking(
     double idle_time_in_ms, size_t size_of_objects,
     size_t final_incremental_mark_compact_speed_in_bytes_per_ms) {
   if (incremental_marking()->IsComplete() ||
-      (incremental_marking()->IsMarkingDequeEmpty() &&
+      (mark_compact_collector_.marking_deque()->IsEmpty() &&
        gc_idle_time_handler_.ShouldDoFinalIncrementalMarkCompact(
            static_cast<size_t>(idle_time_in_ms), size_of_objects,
            final_incremental_mark_compact_speed_in_bytes_per_ms))) {
@@ -5507,7 +5509,6 @@ void Heap::TearDown() {
   }
 
   store_buffer()->TearDown();
-  incremental_marking()->TearDown();
 
   isolate_->memory_allocator()->TearDown();
 }