FULL PRODUCT VERSION :
Java HotSpot(TM) 64-Bit Server VM (build 1.8.0_66-b17, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
This bug seems OS-independent, that is it occur everywhere when screen resolution is 1024*768. We have reproduced it on following:
- Microsoft Windows [Version 6.1.7601]
- Linux 3.16.0-4-amd64 #1 SMP Debian 3.16.7+deb8u3 x86_64 GNU/Linux


EXTRA RELEVANT SYSTEM CONFIGURATION :
The screen resolution should be changed to 1024*768 in order to reproduce this problem. Otherwise, no specific configuration

A DESCRIPTION OF THE PROBLEM :
When a combobox dropdown list is configured with cell size 50 in css, and the screen resolution is 1024*768, the combobox dropdown list will drop out of screen
if the button is placed in the middle of the screen and the visibleRowCount is 9. See the steps for a ready made program to reproduce it.

REGRESSION. Last worked in version 7u80

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Change the screen resolution to 1024*768
2. Compile ComboBoxMisplacementDemo.java together with with style.css


===============================
ComboBoxMisplacementDemo.java
===============================

import javafx.application.Application;
import static javafx.application.Application.launch;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ComboBox;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class ComboBoxMisplacementDemo extends Application {
    
    
    @Override
    public void start(Stage primaryStage) {
        ComboBox<Integer> comboBox = new ComboBox();
        comboBox.setVisibleRowCount(9);
        for(int i = 1; i < 10; i++){
            comboBox.getItems().add(i);
        }
        StackPane root = new StackPane();
        root.getChildren().add(comboBox);
        Scene scene = new Scene(root, 1024, 768);
        scene.getStylesheets().add(ComboBoxMisplacementDemo.class.getResource("/style.css").toExternalForm());
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        launch(args);
    }
    
}


============
style.css
============
.combo-box-popup .list-view .list-cell{
    -fx-cell-size: 50;
}



3. Run the program in the screen resolution 1024*768 and click on the combobox.

4. The dropdown list goes out of the bottom of screen. (9 rows should be visible, but row 8 and 9 are hidden)

5. Click again on the combobox. Now it flickers and suddenly jumps to the top of the screen.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
We expected the combobox dropdown list to behave like JavaFX 2.2, that is, correct its alignment along the bottom line of the screen, and maintain that position. But if it aligns itself to the top it is ok as long as it does that every time.
ACTUAL -
The combobox dropdown list first goes out of screen bounds in the first click, and second click aligns itself to the top of the screen after flickering a bit.

REPRODUCIBILITY :
This bug can be reproduced always.