[Sync] Cleanup all tab sync enabling logic now that its on by default.

BUG=none
TEST=


Review URL: https://chromiumcodereview.appspot.com/10443046

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@139462 0039d316-1c4b-4281-b951-d872f2087c98
void SyncManager::SyncInternal::OnIPAddressChanged() {
  DVLOG(1) << "IP address change detected";
  if (!observing_ip_address_changes_) {
    DVLOG(1) << "IP address change dropped.";
    return;
  }

  OnIPAddressChangedImpl();
}

void SyncManager::SyncInternal::OnIPAddressChanged() {
  DVLOG(1) << "IP address change detected";
  if (!observing_ip_address_changes_) {
    DVLOG(1) << "IP address change dropped.";
    return;
  }

  OnIPAddressChangedImpl();
}
