Simplify pre+post GC ThreadState steps.

third_party/WebKit/Source/platform/heap/Heap.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 377 matching lines @@
                                       const char* typeName);
   template <typename T>
   static Address allocate(size_t, bool eagerlySweep = false);
   template <typename T>
   static Address reallocate(void* previous, size_t);
 
   void processMarkingStack(Visitor*);
   void postMarkingProcessing(Visitor*);
   void weakProcessing(Visitor*);
 
-  void preGC();
-  void postGC(BlinkGC::GCType);
-  void preSweep(BlinkGC::GCType);
-
   // Conservatively checks whether an address is a pointer in any of the
   // thread heaps.  If so marks the object pointed to as live.
   Address checkAndMarkPointer(Visitor*, Address);
 #if DCHECK_IS_ON()
   Address checkAndMarkPointer(Visitor*,
                               Address,
                               MarkedPointerCallbackForTesting);
 #endif
 
   size_t objectPayloadSizeForTesting();
@@ skipping 253 matching lines @@
   T** cell = reinterpret_cast<T**>(object);
   if (*cell && !ObjectAliveTrait<T>::isHeapObjectAlive(*cell))
     *cell = nullptr;
 }
 
 }  // namespace blink
 
 #include "platform/heap/VisitorImpl.h"
 
 #endif  // Heap_h