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::Core::HandleInitalizationCompletedOnFrontendLoop() {
  if (!host_)
    return;
  host_->HandleInitializationCompletedOnFrontendLoop();
}

void SyncBackendHost::Core::HandleInitalizationCompletedOnFrontendLoop() {
  if (!host_)
    return;
  host_->HandleInitializationCompletedOnFrontendLoop();
}
