Enable HistoryModelWorker by default, now that bug 69561 is fixed.

BUG=69561
TEST=Run sync manually and run integration tests, sync should not crash.

Review URL: http://codereview.chromium.org/7016007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@85211 0039d316-1c4b-4281-b951-d872f2087c98
void SyncBackendHost::DeactivateDataType(
    DataTypeController* data_type_controller,
    ChangeProcessor* change_processor) {
  base::AutoLock lock(registrar_lock_);
  registrar_.routing_info.erase(data_type_controller->type());

  change_processor->Stop();
  std::map<syncable::ModelType, ChangeProcessor*>::size_type erased =
      processors_.erase(data_type_controller->type());
  DCHECK_EQ(erased, 1U);
}

void SyncBackendHost::DeactivateDataType(
    DataTypeController* data_type_controller,
    ChangeProcessor* change_processor) {
  base::AutoLock lock(registrar_lock_);
  registrar_.routing_info.erase(data_type_controller->type());

  change_processor->Stop();
  std::map<syncable::ModelType, ChangeProcessor*>::size_type erased =
      processors_.erase(data_type_controller->type());
  DCHECK_EQ(erased, 1U);
}
