Remove GC prologue and epilogue callbacks.

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 RUNTIME_VM_GC_MARKER_H_
 #define RUNTIME_VM_GC_MARKER_H_
 
 #include "vm/allocation.h"
 #include "vm/os_thread.h"  // Mutex.
 
 namespace dart {
 
 // Forward declarations.
 class HandleVisitor;
 class Heap;
 class Isolate;
 class ObjectPointerVisitor;
 class PageSpace;
 class RawWeakProperty;
 
 // The class GCMarker is used to mark reachable old generation objects as part
 // of the mark-sweep collection. The marking bit used is defined in RawObject.
 class GCMarker : public ValueObject {
  public:
   explicit GCMarker(Heap* heap) : heap_(heap), marked_bytes_(0) {}
   ~GCMarker() {}
 
   void MarkObjects(Isolate* isolate,
                    PageSpace* page_space,
-                   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 Prologue(Isolate* isolate);
+  void Epilogue(Isolate* isolate);
   void IterateRoots(Isolate* isolate,
                     ObjectPointerVisitor* visitor,
                     intptr_t slice_index,
                     intptr_t num_slices);
   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  // RUNTIME_VM_GC_MARKER_H_