private void setLastLaunchAccountCount(int accountCount) {
    preferences.edit().putInt(PREF_KEY_LAST_LAUNCH_ACCOUNT_COUNT, accountCount).commit();
  }
Sets the number of accounts in {@link AccountDb} that were there during the most recent launch
of this "page". "Launch" is defined from the pespective of user's actions (starting the app,
performing an operation that changes this page, etc.).
java/com/google/android/apps/authenticator/AuthenticatorActivity.java