- Add and enable concurrent sweeper.

runtime/vm/gc_sweeper.h

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_GC_SWEEPER_H_
 #define VM_GC_SWEEPER_H_
 
 #include "vm/globals.h"
 
 namespace dart {
 
 // Forward declarations.
 class FreeList;
 class Heap;
 class HeapPage;
+class Isolate;
+class PageSpace;
 
 // The class GCSweeper is used to visit the heap after marking to reclaim unused
 // memory.
 class GCSweeper {
  public:
   explicit GCSweeper(Heap* heap) : heap_(heap) {}
   ~GCSweeper() {}
 
   // Sweep the memory area for the page while clearing the mark bits and adding
   // all the unmarked objects to the pre-locked freelist.
   // Returns true if the page is in use.
   bool SweepPage(HeapPage* page, FreeList* freelist);
 
   // Returns the number of words from page->object_start() to the end of the
   // last marked object.
   intptr_t SweepLargePage(HeapPage* page);
 
+  // Sweep the regular sized data pages between first and last inclusive.
+  static void SweepConcurrent(Isolate* isolate,
+                              HeapPage* first,
+                              HeapPage* last,
+                              FreeList* freelist);
+
  private:
   Heap* heap_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(GCSweeper);
 };
 
 }  // namespace dart
 
 #endif  // VM_GC_SWEEPER_H_