Remove support for object grouping during Garbage Collection

runtime/vm/gc_marker.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_MARKER_H_
 #define VM_GC_MARKER_H_
 
 #include "vm/allocation.h"
 #include "vm/os_thread.h"  // Mutex.
 
@@ skipping 20 matching lines @@
                    bool invoke_api_callbacks,
                    bool collect_code);
 
   intptr_t marked_words() { return marked_bytes_ >> kWordSizeLog2; }
 
  private:
   void Prologue(Isolate* isolate, bool invoke_api_callbacks);
   void Epilogue(Isolate* isolate, bool invoke_api_callbacks);
   void IterateRoots(Isolate* isolate,
                     ObjectPointerVisitor* visitor,
-                    bool visit_prologue_weak_persistent_handles,
                     intptr_t slice_index, intptr_t num_slices);
-  void IterateWeakRoots(Isolate* isolate,
-                        HandleVisitor* visitor,
-                        bool visit_prologue_weak_persistent_handles);
+  void IterateWeakRoots(Isolate* isolate, HandleVisitor* visitor);
   template<class MarkingVisitorType>
   void IterateWeakReferences(Isolate* isolate, MarkingVisitorType* visitor);
   void ProcessWeakTables(PageSpace* page_space);
   void ProcessObjectIdTable(Isolate* isolate);
 
   // Called by anyone: finalize and accumulate stats from 'visitor'.
   template<class MarkingVisitorType>
   void FinalizeResultsFrom(MarkingVisitorType* visitor);
 
   Heap* heap_;
 
   Mutex stats_mutex_;
   // TODO(koda): Remove after verifying it's redundant w.r.t. ClassHeapStats.
   uintptr_t marked_bytes_;
 
   friend class MarkTask;
   DISALLOW_IMPLICIT_CONSTRUCTORS(GCMarker);
 };
 
 }  // namespace dart
 
 #endif  // VM_GC_MARKER_H_