Implement prologue weak persistent handles.

runtime/vm/pages.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_PAGES_H_
 #define VM_PAGES_H_
 
 #include "vm/freelist.h"
 #include "vm/globals.h"
 #include "vm/virtual_memory.h"
@@ skipping 69 matching lines @@
   bool IsValidAddress(uword addr) const {
     return Contains(addr);
   }
   static bool IsPageAllocatableSize(intptr_t size) {
     return size <= kAllocatablePageSize;
   }
 
   void VisitObjectPointers(ObjectPointerVisitor* visitor) const;
 
   // Collect the garbage in the page space using mark-sweep.
-  void MarkSweep();
+  void MarkSweep(bool invoke_api_callbacks);
 
   static HeapPage* PageFor(RawObject* raw_obj) {
     return reinterpret_cast<HeapPage*>(
         RawObject::ToAddr(raw_obj) & ~(kPageSize -1));
   }
 
  private:
   static const intptr_t kAllocatablePageSize = kPageSize - sizeof(HeapPage);
 
   void AllocatePage();
@@ skipping 29 matching lines @@
 
   // Keep track whether a MarkSweep is currently running.
   bool sweeping_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(PageSpace);
 };
 
 }  // namespace dart
 
 #endif  // VM_PAGES_H_