Reland "Make sure that memory reducer makes progress in incremental marking""

src/heap/incremental-marking.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/incremental-marking.h"
 
 #include "src/code-stubs.h"
 #include "src/compilation-cache.h"
 #include "src/conversions.h"
 #include "src/heap/gc-tracer.h"
@@ skipping 523 matching lines @@
   // Ready to start incremental marking.
   if (FLAG_trace_incremental_marking) {
     PrintF("[IncrementalMarking] Running\n");
   }
 }
 
 
 void IncrementalMarking::MarkObjectGroups() {
   DCHECK(FLAG_overapproximate_weak_closure);
   DCHECK(!weak_closure_was_overapproximated_);
+  DCHECK(IsMarking());
 
   int old_marking_deque_top =
       heap_->mark_compact_collector()->marking_deque()->top();
 
   heap_->mark_compact_collector()->MarkImplicitRefGroups(&MarkObject);
 
   IncrementalMarkingRootMarkingVisitor visitor(this);
   heap_->isolate()->global_handles()->IterateObjectGroups(
       &visitor, &MarkCompactCollector::IsUnmarkedHeapObjectWithHeap);
 
@@ skipping 457 matching lines @@
 void IncrementalMarking::IncrementIdleMarkingDelayCounter() {
   idle_marking_delay_counter_++;
 }
 
 
 void IncrementalMarking::ClearIdleMarkingDelayCounter() {
   idle_marking_delay_counter_ = 0;
 }
 }  // namespace internal
 }  // namespace v8