Report progress and time taken for JavaFX WebEngine loading

LoadTimer.java

import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.beans.property.*;
import javafx.beans.value.*;
import javafx.concurrent.Worker;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.layout.*;
import javafx.scene.web.*;
import javafx.stage.Stage;

/** Reports load times for pages loaded in a WebView */
public class LoadTimer extends Application {

  public static void main(String[] args) { launch(args); }

  @Override public void start(final Stage stage) {
    final WebView webview  = new WebView();

    VBox layout = new VBox();
    layout.getChildren().setAll(
        createProgressReport(webview.getEngine()),
        webview
    );

    stage.setScene(new Scene(layout));
    stage.show();

    webview.getEngine().load("http://www.fxexperience.com");
  }

  /** @return a HBox containing a ProgressBar bound to engine load progress and a Label showing load times */
  private HBox createProgressReport(WebEngine engine) {
    final LongProperty startTime   = new SimpleLongProperty();
    final LongProperty endTime     = new SimpleLongProperty();
    final LongProperty elapsedTime = new SimpleLongProperty();

    final ProgressBar loadProgress = new ProgressBar();
    loadProgress.progressProperty().bind(engine.getLoadWorker().progressProperty());

    final Label loadTimeLabel = new Label();
    loadTimeLabel.textProperty().bind(
        Bindings.when(
            elapsedTime.greaterThan(0))
              .then(
                  Bindings.concat("Loaded page in ", elapsedTime.divide(1_000_000), "ms")
              )
              .otherwise(
                  "Loading..."
              )
    );

    elapsedTime.bind(Bindings.subtract(endTime, startTime));

    engine.getLoadWorker().stateProperty().addListener(new ChangeListener<Worker.State>() {
      @Override
      public void changed(ObservableValue<? extends Worker.State> observableValue, Worker.State oldState, Worker.State state) {
        switch (state) {
          case RUNNING:
            startTime.set(System.nanoTime());
            break;

          case SUCCEEDED:
            endTime.set(System.nanoTime());
            break;
        }
      }
    });

    HBox progressReport = new HBox(10);
    progressReport.getChildren().setAll(
        loadProgress,
        loadTimeLabel
    );
    progressReport.setPadding(new Insets(5));
    progressReport.setAlignment(Pos.CENTER_LEFT);

    return progressReport;
  }
}