[Sync] Support commit only types.

components/sync/base/model_type.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 COMPONENTS_SYNC_BASE_MODEL_TYPE_H_
 #define COMPONENTS_SYNC_BASE_MODEL_TYPE_H_
 
 #include <map>
 #include <memory>
 #include <ostream>
@@ skipping 227 matching lines @@
 bool IsControlType(ModelType model_type);
 
 // Core types are those data types used by sync's core functionality (i.e. not
 // user data types). These types are always enabled, and include ControlTypes().
 //
 // The set of all core types.
 ModelTypeSet CoreTypes();
 // Those core types that have high priority (includes ControlTypes()).
 ModelTypeSet PriorityCoreTypes();
 
+// Types that may commit data, but should never be included in a GetUpdates.
+ModelTypeSet CommitOnlyTypes();
+
 // Determine a model type from the field number of its associated
 // EntitySpecifics field.  Returns UNSPECIFIED if the field number is
 // not recognized.
 //
 // If you're putting the result in a ModelTypeSet, you should use the
 // following pattern:
 //
 //   ModelTypeSet model_types;
 //   // Say we're looping through a list of items, each of which has a
 //   // field number.
@@ skipping 91 matching lines @@
 
 // Returns true if |model_type| supports parent-child hierarchy or entries.
 bool TypeSupportsHierarchy(ModelType model_type);
 
 // Returns true if |model_type| supports ordering of sibling entries.
 bool TypeSupportsOrdering(ModelType model_type);
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_BASE_MODEL_TYPE_H_