[heap] Fix condition for usage of concurrent marking deque.

src/heap/heap.cc

 // 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.
 
 #include "src/heap/heap.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/assembler-inl.h"
 #include "src/ast/context-slot-cache.h"
@@ skipping 5487 matching lines @@
   for (int i = 0; i < static_cast<int>(v8::Isolate::kUseCounterFeatureCount);
        i++) {
     deferred_counters_[i] = 0;
   }
 
   tracer_ = new GCTracer(this);
   scavenge_collector_ = new Scavenger(this);
   mark_compact_collector_ = new MarkCompactCollector(this);
   incremental_marking_->set_marking_deque(
       mark_compact_collector_->marking_deque());
+#if V8_CONCURRENT_MARKING
   concurrent_marking_ =
       new ConcurrentMarking(this, mark_compact_collector_->marking_deque());
+#else
+  concurrent_marking_ = new ConcurrentMarking(this, nullptr);
+#endif
   if (FLAG_minor_mc)
     minor_mark_compact_collector_ = new MinorMarkCompactCollector(this);
   gc_idle_time_handler_ = new GCIdleTimeHandler();
   memory_reducer_ = new MemoryReducer(this);
   if (V8_UNLIKELY(FLAG_gc_stats)) {
     live_object_stats_ = new ObjectStats(this);
     dead_object_stats_ = new ObjectStats(this);
   }
   scavenge_job_ = new ScavengeJob();
   local_embedder_heap_tracer_ = new LocalEmbedderHeapTracer();
@@ skipping 859 matching lines @@
     case LO_SPACE:
       return "LO_SPACE";
     default:
       UNREACHABLE();
   }
   return NULL;
 }
 
 }  // namespace internal
 }  // namespace v8