FULL PRODUCT VERSION :
java version "1.8.0_40"
Java(TM) SE Runtime Environment (build 1.8.0_40-b26)
Java HotSpot(TM) 64-Bit Server VM (build 25.40-b25, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
When a ComboBox is deactivated programmatically with

comboBox.setDisable(true);

then the tooltip is not displayed anymore. This is necessary since the size of a ComboBox can extend the area it is displayed. Selected items cannot be read then anymore. We regard this as a general bug since other controls (e.g. TextField) show the same behaviour.

ADDITIONAL REGRESSION INFORMATION:
java version "1.8.0_40"
Java(TM) SE Runtime Environment (build 1.8.0_40-b26)
Java HotSpot(TM) 64-Bit Server VM (build 25.40-b25, mixed mode)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1.) generate a ComboBox with items
2.) generate a Tooltip and set it on the combBox generated in step 1
3.) disable the comboBox
4.) start the program and verify the tooltip does not pop up

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The tooltip should be displayed
ACTUAL -
No tooltip is shown when the control is disabled

REPRODUCIBILITY :
This bug can be reproduced always.