This issue was introduced in RT-31283

To reproduce this issue run HelloComboBox and click on any combobox except first one.

Exception in thread "JavaFX Application Thread" java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(HashMap.java:2395)
at java.util.HashMap$EntryIterator.next(HashMap.java:2466)
at java.util.HashMap$EntryIterator.next(HashMap.java:2464)
at javafx.scene.CssStyleHelper.resetToInitialValues(CssStyleHelper.java:280)
at javafx.scene.CssStyleHelper.createStyleHelper(CssStyleHelper.java:95)
at javafx.scene.Node.impl_processCSS(Node.java:8620)
at javafx.scene.Parent.impl_processCSS(Parent.java:1205)
at javafx.scene.control.Control.impl_processCSS(Control.java:863)
at javafx.scene.Parent.impl_processCSS(Parent.java:1217)
at javafx.scene.control.PopupControl$CSSBridge.impl_processCSS(PopupControl.java:1204)
at javafx.scene.Parent.impl_processCSS(Parent.java:1217)
at javafx.scene.Node.processCSS(Node.java:8549)
at javafx.scene.Scene.doCSSPass(Scene.java:538)
at javafx.scene.Scene.preferredSize(Scene.java:1504)
at javafx.scene.Scene.impl_preferredSize(Scene.java:1571)
at javafx.stage.Window$9.invalidated(Window.java:730)
at javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:109)
at javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:143)
at javafx.stage.Window.setShowing(Window.java:796)
at javafx.stage.Window.show(Window.java:811)
at javafx.stage.PopupWindow.showImpl(PopupWindow.java:403)
at javafx.stage.PopupWindow.show(PopupWindow.java:367)
at com.sun.javafx.scene.control.skin.ComboBoxPopupControl.positionAndShowPopup(ComboBoxPopupControl.java:101)
at com.sun.javafx.scene.control.skin.ComboBoxPopupControl.show(ComboBoxPopupControl.java:79)
at com.sun.javafx.scene.control.skin.ComboBoxBaseSkin.handleControlPropertyChanged(ComboBoxBaseSkin.java:116)
at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin.handleControlPropertyChanged(ComboBoxListViewSkin.java:219)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$2.call(BehaviorSkinBase.java:179)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$2.call(BehaviorSkinBase.java:177)
at com.sun.javafx.scene.control.MultiplePropertyChangeListenerHandler$1.changed(MultiplePropertyChangeListenerHandler.java:55)
at javafx.beans.value.WeakChangeListener.changed(WeakChangeListener.java:88)
at com.sun.javafx.binding.ExpressionHelper$SingleChange.fireValueChangedEvent(ExpressionHelper.java:176)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.beans.property.ReadOnlyBooleanWrapper$ReadOnlyPropertyImpl.fireValueChangedEvent(ReadOnlyBooleanWrapper.java:178)
at javafx.beans.property.ReadOnlyBooleanWrapper$ReadOnlyPropertyImpl.access$100(ReadOnlyBooleanWrapper.java:148)
at javafx.beans.property.ReadOnlyBooleanWrapper.fireValueChangedEvent(ReadOnlyBooleanWrapper.java:144)
at javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:110)
at javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:143)
at javafx.scene.control.ComboBoxBase.setShowing(ComboBoxBase.java:188)
at javafx.scene.control.ComboBoxBase.show(ComboBoxBase.java:393)
at com.sun.javafx.scene.control.behavior.ComboBoxBaseBehavior.show(ComboBoxBaseBehavior.java:247)
at com.sun.javafx.scene.control.behavior.ComboBoxBaseBehavior.mouseReleased(ComboBoxBaseBehavior.java:205)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:91)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:84)
at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:203)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3544)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3375)
at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3327)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1618)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2395)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:312)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:237)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:354)
at com.sun.glass.ui.View.handleMouseEvent(View.java:514)
at com.sun.glass.ui.View.notifyMouse(View.java:877)
at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at com.sun.glass.ui.gtk.GtkApplication.access$200(GtkApplication.java:47)
at com.sun.glass.ui.gtk.GtkApplication$5$1.run(GtkApplication.java:137)
at java.lang.Thread.run(Thread.java:724)
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at com.sun.javafx.binding.ExpressionHelper.removeListener(ExpressionHelper.java:73)
at javafx.beans.property.ReadOnlyBooleanWrapper$ReadOnlyPropertyImpl.removeListener(ReadOnlyBooleanWrapper.java:174)
at javafx.stage.PopupWindow.unbindOwnerFocusedProperty(PopupWindow.java:640)
at javafx.stage.PopupWindow.impl_visibleChanged(PopupWindow.java:466)
at javafx.stage.Window$9.invalidated(Window.java:781)
at javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:109)
at javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:143)
at javafx.stage.Window.setShowing(Window.java:796)
at javafx.stage.Window.hide(Window.java:821)
at javafx.stage.PopupWindow.hide(PopupWindow.java:417)
at com.sun.javafx.scene.control.skin.ComboBoxPopupControl.hide(ComboBoxPopupControl.java:84)
at com.sun.javafx.scene.control.skin.ComboBoxBaseSkin.handleControlPropertyChanged(ComboBoxBaseSkin.java:118)
at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin.handleControlPropertyChanged(ComboBoxListViewSkin.java:219)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$2.call(BehaviorSkinBase.java:179)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$2.call(BehaviorSkinBase.java:177)
at com.sun.javafx.scene.control.MultiplePropertyChangeListenerHandler$1.changed(MultiplePropertyChangeListenerHandler.java:55)
at javafx.beans.value.WeakChangeListener.changed(WeakChangeListener.java:88)
at com.sun.javafx.binding.ExpressionHelper$SingleChange.fireValueChangedEvent(ExpressionHelper.java:176)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.beans.property.ReadOnlyBooleanWrapper$ReadOnlyPropertyImpl.fireValueChangedEvent(ReadOnlyBooleanWrapper.java:178)
at javafx.beans.property.ReadOnlyBooleanWrapper$ReadOnlyPropertyImpl.access$100(ReadOnlyBooleanWrapper.java:148)
at javafx.beans.property.ReadOnlyBooleanWrapper.fireValueChangedEvent(ReadOnlyBooleanWrapper.java:144)
at javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:110)
at javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:143)
at javafx.scene.control.ComboBoxBase.setShowing(ComboBoxBase.java:188)
at javafx.scene.control.ComboBoxBase.hide(ComboBoxBase.java:402)
at com.sun.javafx.scene.control.skin.ComboBoxBaseSkin.focusLost(ComboBoxBaseSkin.java:88)
at com.sun.javafx.scene.control.skin.ComboBoxBaseSkin$1.changed(ComboBoxBaseSkin.java:75)
at com.sun.javafx.scene.control.skin.ComboBoxBaseSkin$1.changed(ComboBoxBaseSkin.java:72)
at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:347)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.beans.property.ReadOnlyBooleanPropertyBase.fireValueChangedEvent(ReadOnlyBooleanPropertyBase.java:72)
at javafx.scene.Node$FocusedProperty.notifyListeners(Node.java:7328)
at javafx.scene.Node.setFocused(Node.java:7379)
at javafx.scene.Scene$KeyHandler.setWindowFocused(Scene.java:3701)
at javafx.scene.Scene$KeyHandler$1.invalidated(Scene.java:3720)
at com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:135)
at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.beans.property.ReadOnlyBooleanWrapper$ReadOnlyPropertyImpl.fireValueChangedEvent(ReadOnlyBooleanWrapper.java:178)
at javafx.beans.property.ReadOnlyBooleanWrapper$ReadOnlyPropertyImpl.access$100(ReadOnlyBooleanWrapper.java:148)
at javafx.beans.property.ReadOnlyBooleanWrapper.fireValueChangedEvent(ReadOnlyBooleanWrapper.java:144)
at javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:110)
at javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:143)
at javafx.stage.Window.setFocused(Window.java:387)
at com.sun.javafx.stage.WindowPeerListener.changedFocused(WindowPeerListener.java:59)
at com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:89)
at com.sun.javafx.tk.quantum.GlassWindowEventHandler.run(GlassWindowEventHandler.java:39)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassWindowEventHandler.handleWindowEvent(GlassWindowEventHandler.java:130)
at com.sun.glass.ui.Window.handleWindowEvent(Window.java:1239)
at com.sun.glass.ui.Window.notifyFocus(Window.java:1214)
at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at com.sun.glass.ui.gtk.GtkApplication.access$200(GtkApplication.java:47)
at com.sun.glass.ui.gtk.GtkApplication$5$1.run(GtkApplication.java:137)
at java.lang.Thread.run(Thread.java:724)