sync: Implementation of Priority Preferences.

sync/syncable/model_type.cc

Index: sync/syncable/model_type.cc
diff --git a/sync/syncable/model_type.cc b/sync/syncable/model_type.cc
index 37bdd361ac3abd2d86053cd7ca59cd08688cf9c9..31120a78e71391ee14e86bf31147626ce1dc14b1 100644
--- a/sync/syncable/model_type.cc
+++ b/sync/syncable/model_type.cc
@@ -353,6 +353,9 @@ ModelTypeSet EncryptableUserTypes() {
   encryptable_user_types.Remove(HISTORY_DELETE_DIRECTIVES);
   // Synced notifications are not encrypted since the server must see changes.
   encryptable_user_types.Remove(SYNCED_NOTIFICATIONS);
+  // Priority preferences are not encrypted because they might be synced before
+  // encryption is ready.
+  encryptable_user_types.RemoveAll(PriorityUserTypes());
   // Proxy types have no sync representation and are therefore not encrypted.
   // Note however that proxy types map to one or more protocol types, which
   // may or may not be encrypted themselves.
@@ -360,6 +363,10 @@ ModelTypeSet EncryptableUserTypes() {
   return encryptable_user_types;
 }
 
+ModelTypeSet PriorityUserTypes() {
+  return ModelTypeSet(PRIORITY_PREFERENCES);
+}
+
 ModelTypeSet ControlTypes() {
   ModelTypeSet set;
   // TODO(sync): We should be able to build the actual enumset's internal
@@ -369,9 +376,6 @@ ModelTypeSet ControlTypes() {
     set.Put(ModelTypeFromInt(i));
   }
 
-  // TODO(albertb): Re-enable this when the server supports it.
-  set.Remove(PRIORITY_PREFERENCES);
-
   return set;
 }