[Sync] Replace typedef with using.

components/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 COMPONENTS_SYNC_SYNCABLE_PARENT_CHILD_INDEX_H_
 #define COMPONENTS_SYNC_SYNCABLE_PARENT_CHILD_INDEX_H_
 
 #include <map>
 #include <memory>
 #include <set>
 #include <vector>
 
 #include "base/macros.h"
 #include "components/sync/base/model_type.h"
 #include "components/sync/syncable/syncable_id.h"
 
 namespace syncer {
 namespace syncable {
 
 struct EntryKernel;
 class ParentChildIndex;
 
 // A node ordering function.
 struct ChildComparator {
   bool operator()(const EntryKernel* a, const EntryKernel* b) const;
 };
 
 // An ordered set of nodes.
-typedef std::set<EntryKernel*, ChildComparator> OrderedChildSet;
-typedef std::shared_ptr<OrderedChildSet> OrderedChildSetRef;
+using OrderedChildSet = std::set<EntryKernel*, ChildComparator>;
+using OrderedChildSetRef = std::shared_ptr<OrderedChildSet>;
 
 // Container that tracks parent-child relationships.
 // Provides fast lookup of all items under a given parent.
 class ParentChildIndex {
  public:
   ParentChildIndex();
   ~ParentChildIndex();
 
   // Returns whether or not this entry belongs in the index.
   // True for all non-deleted, non-root entries.
@@ skipping 18 matching lines @@
 
   // Returns all siblings of the entry.
   const OrderedChildSet* GetSiblings(EntryKernel* e) const;
 
   // Estimates amount of heap memory used.
   size_t EstimateMemoryUsage() const;
 
  private:
   friend class ParentChildIndexTest;
 
-  typedef std::map<Id, OrderedChildSetRef> ParentChildrenMap;
-  typedef std::vector<Id> TypeRootIds;
-  typedef std::vector<OrderedChildSetRef> TypeRootChildSets;
+  using ParentChildrenMap = std::map<Id, OrderedChildSetRef>;
+  using TypeRootIds = std::vector<Id>;
+  using TypeRootChildSets = std::vector<OrderedChildSetRef>;
 
   static bool ShouldUseParentId(const Id& parent_id, ModelType model_type);
 
   // Returns OrderedChildSet that should contain the specified entry
   // based on the entry's Parent ID or model type.
   const OrderedChildSetRef GetChildSet(EntryKernel* e) const;
 
   // Returns OrderedChildSet that contain entries of the |model_type| type.
   const OrderedChildSetRef GetModelTypeChildSet(ModelType model_type) const;
 
@@ skipping 16 matching lines @@
   // with implicit parent.
   TypeRootChildSets type_root_child_sets_;
 
   DISALLOW_COPY_AND_ASSIGN(ParentChildIndex);
 };
 
 }  // namespace syncable
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_SYNCABLE_PARENT_CHILD_INDEX_H_