[WIP][tracing] Add memory dump provider for sync Directory

sync/syncable/parent_child_index.h

 // Copyright (c) 2012 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_PARENT_CHILD_INDEX_H_
 #define SYNC_SYNCABLE_PARENT_CHILD_INDEX_H_
 
 #include <map>
 #include <set>
 #include <vector>
@@ skipping 42 matching lines @@
   // node has no children or the Id does not identify a valid directory node.
   const OrderedChildSet* GetChildren(const Id& id) const;
 
   // Returns all children of the entry.  Returns NULL if the node has no
   // children.
   const OrderedChildSet* GetChildren(EntryKernel* e) const;
 
   // Returns all siblings of the entry.
   const OrderedChildSet* GetSiblings(EntryKernel* e) const;
 
+  // Returns the memory usage of the index.
+  size_t bytes_used() const { return bytes_used_; }
+
  private:
   friend class ParentChildIndexTest;
 
   typedef std::map<Id, OrderedChildSet*> ParentChildrenMap;
   typedef std::vector<Id> TypeRootIds;
   typedef ScopedVector<OrderedChildSet> TypeRootChildSets;
 
   static bool ShouldUseParentId(const Id& parent_id, ModelType model_type);
 
   // Returns OrderedChildSet that should contain the specified entry
@@ skipping 15 matching lines @@
   ParentChildrenMap parent_children_map_;
 
   // This array tracks model type roots IDs.
   TypeRootIds model_type_root_ids_;
 
   // This array contains pre-defined child sets for
   // non-hierarchical types (types with flat hierarchy) that support entries
   // with implicit parent.
   TypeRootChildSets type_root_child_sets_;
 
+  // Stores the current memory usage of the objects.
+  size_t bytes_used_;
+
   DISALLOW_COPY_AND_ASSIGN(ParentChildIndex);
 };
 
 }  // namespace syncable
 }  // namespace syncer
 
 #endif  // SYNC_SYNCABLE_PARENT_CHILD_INDEX_H_