Make sure that memory reducer makes progress in incremental marking

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 849 matching lines @@
 
   // Performs incremental marking steps of step_size_in_bytes as long as
   // deadline_ins_ms is not reached. step_size_in_bytes can be 0 to compute
   // an estimate increment. Returns the remaining time that cannot be used
   // for incremental marking anymore because a single step would exceed the
   // deadline.
   double AdvanceIncrementalMarking(
       intptr_t step_size_in_bytes, double deadline_in_ms,
       IncrementalMarking::StepActions step_actions);
 
+  void FinalizeIncrementalMarkingIfComplete(const char* comment);
+
   inline void increment_scan_on_scavenge_pages() {
     scan_on_scavenge_pages_++;
     if (FLAG_gc_verbose) {
       PrintF("Scan-on-scavenge pages: %d\n", scan_on_scavenge_pages_);
     }
   }
 
   inline void decrement_scan_on_scavenge_pages() {
     scan_on_scavenge_pages_--;
     if (FLAG_gc_verbose) {
@@ skipping 763 matching lines @@
   // prepared by finishing the previous one.
   void PrepareArrayBufferDiscoveryInNewSpace();
 
   // An ArrayBuffer moved from new space to old space.
   void PromoteArrayBuffer(Object* buffer);
 
   bool HasLowAllocationRate();
   bool HasHighFragmentation();
   bool HasHighFragmentation(intptr_t used, intptr_t committed);
 
+  bool ShouldOptimizeForMemoryUsage() { return optimize_for_memory_usage_; }
+
  protected:
   // Methods made available to tests.
 
   // Allocates a JS Map in the heap.
   MUST_USE_RESULT AllocationResult
       AllocateMap(InstanceType instance_type, int instance_size,
                   ElementsKind elements_kind = TERMINAL_FAST_ELEMENTS_KIND);
 
   // Allocates and initializes a new JavaScript object based on a
   // constructor.
@@ skipping 1180 matching lines @@
   DisallowHeapAllocation no_allocation;  // i.e. no gc allowed.
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PathTracer);
 };
 #endif  // DEBUG
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_HEAP_H_