Sync: Support nodes with implicit permanent folders: Node Browser and out-of-order loading from DB

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
 #define SYNC_SYNCABLE_PARENT_CHILD_INDEX
 
 #include <map>
 #include <set>
 
@@ skipping 42 matching lines @@
 
   // 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;
 
  private:
   friend class ParentChildIndexTest;
+
   typedef std::map<Id, OrderedChildSet*> ParentChildrenMap;
+  typedef std::vector<Id> TypeRootIds;
+  typedef std::vector<OrderedChildSet*> TypeRootChildSets;
 
-  // Determines entry's model type.
-  static ModelType GetModelType(EntryKernel* e);
+  static bool ShouldUseParentId(const Id& parent_id, ModelType model_type);
 
-  // Returns parent ID for the entry which is either its PARENT_ID value
-  // or derived from its model type.
-  const Id& GetParentId(EntryKernel* e) const;
+  // Returns OrderedChildSet that should contain the specified entry
+  // based on the entry's Parent ID or model type.
+  const OrderedChildSet* GetChildSet(EntryKernel* e) const;
+
+  // Returns OrderedChildSet that contain entries of the |model_type| type.
+  const OrderedChildSet* GetModelTypeChildSet(ModelType model_type) const;
+
+  // Returns mutable OrderedChildSet that contain entries of the |model_type|
+  // type. Create one as necessary.
+  OrderedChildSet* GetOrCreateModelTypeChildSet(ModelType model_type);
 
   // Returns previously cached model type root ID for the given |model_type|.
   const Id& GetModelTypeRootId(ModelType model_type) const;
 
   // A map of parent IDs to children.
   // Parents with no children are not included in this map.
   ParentChildrenMap parent_children_map_;
 
   // This array tracks model type roots IDs.
-  Id model_type_root_ids_[MODEL_TYPE_COUNT];
+  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_;
 
   DISALLOW_COPY_AND_ASSIGN(ParentChildIndex);
 };
 
 }  // namespace syncable
 }  // namespace syncer
 
 #endif  // SYNC_SYNCABLE_PARENT_CHILD_INDEX