Reland "[heap] Start sweeper tasks after evacuation" (second try).

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 2299 matching lines @@
 
   // The depth of HeapIterator nestings.
   int heap_iterator_depth_;
 
   EmbedderHeapTracer* embedder_heap_tracer_;
   EmbedderReachableReferenceReporter* embedder_reference_reporter_;
   std::vector<std::pair<void*, void*>> wrappers_to_trace_;
 
   // Used for testing purposes.
   bool force_oom_;
+  bool delay_sweeper_tasks_for_testing_;
 
   // Classes in "heap" can be friends.
   friend class AlwaysAllocateScope;
   friend class GCCallbacksScope;
   friend class GCTracer;
   friend class HeapIterator;
   friend class IdleScavengeObserver;
   friend class IncrementalMarking;
   friend class IncrementalMarkingJob;
   friend class IteratePromotedObjectsVisitor;
@@ skipping 314 matching lines @@
   }
 
  private:
   Heap* heap_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_