[Sync] Clean up ModelType code.

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 73 matching lines @@
   // An object representing a browser session.
   SESSIONS,
   // An app object.
   APPS,
   // An app setting from the extension settings API.
   APP_SETTINGS,
   // An extension setting from the extension settings API.
   EXTENSION_SETTINGS,
   // App notifications.
   APP_NOTIFICATIONS,  // Deprecated.
-  // History delete directives.
+                      // History delete directives.

[pavely, 2017/02/23 23:23:03]

Seems like git cl format messed up indentation.

[skym, 2017/02/24 18:59:07]

It does. I've moved the Deprecated text onto the lines above to avoid this.

   HISTORY_DELETE_DIRECTIVES,
   // Synced push notifications.
   SYNCED_NOTIFICATIONS,  // Deprecated.
-  // Synced Notification app info.
+                         // Synced Notification app info.
   SYNCED_NOTIFICATION_APP_INFO,  // Deprecated.
-  // Custom spelling dictionary.
+                                 // Custom spelling dictionary.
   DICTIONARY,
   // Favicon images.
   FAVICON_IMAGES,
   // Favicon tracking information.
   FAVICON_TRACKING,
   // Client-specific metadata, synced before other user types.
   DEVICE_INFO,
   // These preferences are synced before other user types and are never
   // encrypted.
   PRIORITY_PREFERENCES,
@@ skipping 43 matching lines @@
   EXPERIMENTS,
   LAST_CONTROL_MODEL_TYPE = EXPERIMENTS,
   LAST_REAL_MODEL_TYPE = LAST_CONTROL_MODEL_TYPE,
 
   // If you are adding a new sync datatype that is exposed to the user via the
   // sync preferences UI, be sure to update the list in
   // components/sync/driver/user_selectable_sync_type.h so that the UMA
   // histograms for sync include your new type.  In this case, be sure to also
   // update the UserSelectableTypes() definition in
   // sync/syncable/model_type.cc.
+
+  // Additionally, enum SyncModelTypes and suffix SyncModelType need to be
+  // updated in histograms.xml for all new types.
   MODEL_TYPE_COUNT,
 };
 
 using ModelTypeSet =
     EnumSet<ModelType, FIRST_REAL_MODEL_TYPE, LAST_REAL_MODEL_TYPE>;
 using FullModelTypeSet = EnumSet<ModelType, UNSPECIFIED, LAST_REAL_MODEL_TYPE>;
 using ModelTypeNameMap = std::map<ModelType, const char*>;
 
 inline ModelType ModelTypeFromInt(int i) {
   DCHECK_GE(i, 0);
   DCHECK_LT(i, MODEL_TYPE_COUNT);
   return static_cast<ModelType>(i);
 }
 
-// Used by tests outside of sync/.
-void AddDefaultFieldValue(ModelType datatype,
-                          sync_pb::EntitySpecifics* specifics);
+// Used to mark the type of EntitySpecifics that has no actual data.
+void AddDefaultFieldValue(ModelType type, sync_pb::EntitySpecifics* specifics);
 
 // Extract the model type of a SyncEntity protocol buffer.  ModelType is a
 // local concept: the enum is not in the protocol.  The SyncEntity's ModelType
 // is inferred from the presence of particular datatype field in the
 // entity specifics.
 ModelType GetModelType(const sync_pb::SyncEntity& sync_entity);
 
 // Extract the model type from an EntitySpecifics field.  Note that there
 // are some ModelTypes (like TOP_LEVEL_FOLDER) that can't be inferred this way;
 // prefer using GetModelType where possible.
@@ skipping 157 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_