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
/**
	 * Internal implementation class for a change listener.
	 * @since 3.0
	 */
	protected abstract class AbstractSelectionChangedListener implements ISelectionChangedListener  {
		/**
		 * Installs this selection changed listener with the given selection provider. If
		 * the selection provider is a post selection provider, post selection changed
		 * events are the preferred choice, otherwise normal selection changed events
		 * are requested.
		 * 
		 * @param selectionProvider
		 */
		public void install(ISelectionProvider selectionProvider) {
			if (selectionProvider == null)
				return;