Revert of Sync: MutableEntry shouldn't track changes that have no actual impact on the stored data

sync/syncable/model_neutral_mutable_entry.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SYNC_SYNCABLE_MODEL_NEUTRAL_MUTABLE_ENTRY_H_
 #define SYNC_SYNCABLE_MODEL_NEUTRAL_MUTABLE_ENTRY_H_
 
 #include "sync/base/sync_export.h"
 #include "sync/internal_api/public/base/model_type.h"
 #include "sync/syncable/entry.h"
@@ skipping 82 matching lines @@
 
   // This is similar to what one would expect from Put(TRANSACTION_VERSION),
   // except that it doesn't bother to invoke 'SaveOriginals'.  Calling that
   // function is at best unnecessary, since the transaction will have already
   // used its list of mutations by the time this function is called.
   void UpdateTransactionVersion(int64 version);
 
  protected:
   explicit ModelNeutralMutableEntry(BaseWriteTransaction* trans);
 
-  void MarkDirty();
+  syncable::MetahandleSet* GetDirtyIndexHelper();
 
  private:
   friend class syncer::WriteNode;
   friend class Directory;
 
   // Don't allow creation on heap, except by sync API wrappers.
   void* operator new(size_t size) { return (::operator new)(size); }
 
   // Kind of redundant. We should reduce the number of pointers
   // floating around if at all possible. Could we store this in Directory?
   // Scope: Set on construction, never changed after that.
   BaseWriteTransaction* const base_write_transaction_;
 
   DISALLOW_COPY_AND_ASSIGN(ModelNeutralMutableEntry);
 };
 
 }  // namespace syncable
 }  // namespace syncer
 
 #endif  // SYNC_SYNCABLE_MODEL_NEUTRAL_MUTABLE_ENTRY_H_