Bug 81983 [preferences] Disabling and enabling folding on small file takes forever
3.1 M4 Using enable/disable folding on a small CU takes forever. This is caused by the recent change to apply the preference to all Java editors. In another (hidden) window (Debug) I had StyledText open which (understandably) took long to react on the preference change. Non-visible editor's should not react to this change until they become visible.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/JavaEditor.java
/**
		 * A property change event filter.
		 */
		public interface IPropertyChangeEventFilter {
			/**
			 * Should the given event be filtered?
			 * @param event The property change event.
			 * @return <code>true</code> iff the given event should be filtered.
			 */
			public boolean isFiltered(PropertyChangeEvent event);
		}
		/**
		 * Property change listener. Listens for events in the options Map and
		 * fires a {@link org.eclipse.jface.util.PropertyChangeEvent}
		 * on this adapter with arguments from the received event.
		 */
		private class PropertyChangeListener implements IPropertyChangeListener {