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

src/heap/spaces.h

 // Copyright 2011 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_SPACES_H_
 #define V8_HEAP_SPACES_H_
 
 #include <list>
 #include <memory>
 #include <unordered_set>
@@ skipping 393 matching lines @@
   // Checks whether |addr| can be a limit of addresses in this page. It's a
   // limit if it's in the page, or if it's just after the last byte of the page.
   bool ContainsLimit(Address addr) {
     return addr >= area_start() && addr <= area_end();
   }
 
   base::AtomicValue<ConcurrentSweepingState>& concurrent_sweeping_state() {
     return concurrent_sweeping_;
   }
 
+  bool SweepingDone() {
+    return concurrent_sweeping_state().Value() == kSweepingDone;
+  }
+
   // Manage live byte count, i.e., count of bytes in black objects.
   inline void ResetLiveBytes();
   inline void IncrementLiveBytes(int by);
 
   int LiveBytes() {
     DCHECK_LE(static_cast<unsigned>(live_byte_count_), size_);
     return live_byte_count_;
   }
 
   void SetLiveBytes(int live_bytes) {
@@ skipping 304 matching lines @@
 
   // WaitUntilSweepingCompleted only works when concurrent sweeping is in
   // progress. In particular, when we know that right before this call a
   // sweeper thread was sweeping this page.
   void WaitUntilSweepingCompleted() {
     mutex_->Lock();
     mutex_->Unlock();
     DCHECK(SweepingDone());
   }
 
-  bool SweepingDone() {
-    return concurrent_sweeping_state().Value() == kSweepingDone;
-  }
-
   void ResetFreeListStatistics();
 
   size_t AvailableInFreeList();
 
   size_t LiveBytesFromFreeList() {
     DCHECK_GE(area_size(), wasted_memory() + available_in_free_list());
     return area_size() - wasted_memory() - available_in_free_list();
   }
 
   FreeListCategory* free_list_category(FreeListCategoryType type) {
@@ skipping 2149 matching lines @@
   PageIterator old_iterator_;
   PageIterator code_iterator_;
   PageIterator map_iterator_;
   LargePageIterator lo_iterator_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_SPACES_H_