sync: Add ControlPreference protobuf and supporting code

sync/internal_api/public/base_node.h

 // Copyright 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_INTERNAL_API_PUBLIC_BASE_NODE_H_
 #define SYNC_INTERNAL_API_PUBLIC_BASE_NODE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 143 matching lines @@
   const sync_pb::SessionSpecifics& GetSessionSpecifics() const;
 
   // Getter specific to the DEVICE_INFO datatype.  Returns protobuf
   // data.  Can only be called if GetModelType() == DEVICE_INFO.
   const sync_pb::DeviceInfoSpecifics& GetDeviceInfoSpecifics() const;
 
   // Getter specific to the EXPERIMENTS datatype.  Returns protobuf
   // data.  Can only be called if GetModelType() == EXPERIMENTS.
   const sync_pb::ExperimentsSpecifics& GetExperimentsSpecifics() const;
 
+  // Getter specific to the PRIORITY_PREFERENCE datatype. Returns protobuf
+  // data.  Can only be called if GetModelType() == PRIORITY_PREFERENCE.
+  const sync_pb::PriorityPreferenceSpecifics&
+      GetPriorityPreferenceSpecifics() const;
+
   const sync_pb::EntitySpecifics& GetEntitySpecifics() const;
 
   // Returns the local external ID associated with the node.
   int64 GetExternalId() const;
 
   // Returns true iff this node has children.
   bool HasChildren() const;
 
   // Return the ID of the node immediately before this in the sibling order.
   // For the first node in the ordering, return 0.
@@ skipping 68 matching lines @@
 
   // Same as |unencrypted_data_|, but for legacy password encryption.
   scoped_ptr<sync_pb::PasswordSpecificsData> password_data_;
 
   DISALLOW_COPY_AND_ASSIGN(BaseNode);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_BASE_NODE_H_