Added Privacy section to AutofillService documentation.

 *  AutofillValue password = passwordNode.getAutofillValue().getTextValue().toString();

 *

 *  save(username, password);

 *

 * </pre>

 *

 *

 * <a name="Privacy"></a>

 * <h3>Privacy</h3>

 *

 * <p>The {@link #onFillRequest(FillRequest, CancellationSignal, FillCallback)} method is called

 * without the user content. The Android system strips some properties of the

 * {@link android.app.assist.AssistStructure.ViewNode view nodes} passed to these calls, but not all

 * of them. For example, the data provided in the {@link android.view.ViewStructure.HtmlInfo}

 * objects set by {@link android.webkit.WebView} is never stripped out.

 *

 * <p>Because this data could contain PII (Personally Identifiable Information, such as username or

 * email address), the service should only use it locally (i.e., in the app's process) for

 * heuristics purposes, but it should not be sent to external servers.

 */

public abstract class AutofillService extends Service {

    private static final String TAG = "AutofillService";

     * <p>For example, an HTML form with 2 fields for username and password:

     *

     * <pre class="prettyprint">

     *    <label>Username:</label>

     *    <input type="text" name="username" id="user" value="Type your username" autocomplete="username" placeholder="Email or username">

     *    <label>Password:</label>

     *    <input type="password" name="password" id="pass" autocomplete="current-password" placeholder="Password">

     * </pre>

     *

     *     username.setHtmlInfo(username.newHtmlInfoBuilder("input")

     *         .addAttribute("type", "text")

     *         .addAttribute("name", "username")

     *         .addAttribute("label", "Username:")

     *         .build());

     *     username.setHint("Email or username");

     *     username.setAutofillType(View.AUTOFILL_TYPE_TEXT);

     *     password.setHtmlInfo(password.newHtmlInfoBuilder("input")

     *         .addAttribute("type", "password")

     *         .addAttribute("name", "password")

     *         .addAttribute("label", "Password:")

     *         .build());

     *     password.setHint("Password");

     *     password.setAutofillType(View.AUTOFILL_TYPE_TEXT);