static X509TrustManager getDefaultX509TrustManager() throws KeyManagementException {
        X509TrustManager result = defaultX509TrustManager;
        if (result == null) {
            // single-check idiom
            defaultX509TrustManager = result = createDefaultX509TrustManager();
        }
        return result;
    }
Returns X.509 key manager or null for none.
common/src/main/java/org/conscrypt/SSLParametersImpl.java