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
* @see org.eclipse.ui.texteditor.AbstractTextEditor#setPreferenceStore(org.eclipse.jface.preference.IPreferenceStore)
	 * @since 3.0
	 */
	protected void setPreferenceStore(IPreferenceStore store) {
		super.setPreferenceStore(store);
		if (getSourceViewerConfiguration() instanceof JavaSourceViewerConfiguration) {
			JavaTextTools textTools= JavaPlugin.getDefault().getJavaTextTools();
			setSourceViewerConfiguration(new JavaSourceViewerConfiguration(textTools.getColorManager(), store, this, IJavaPartitions.JAVA_PARTITIONING));
		}
		if (getSourceViewer() instanceof JavaSourceViewer)
			((JavaSourceViewer)getSourceViewer()).setPreferenceStore(store);
	}
	
	/*
	 * @see IWorkbenchPart#dispose()
	 */
	public void dispose() {
		
		if (fProjectionModelUpdater != null) {
			fProjectionModelUpdater.uninstall();
			fProjectionModelUpdater= null;
		}
		
		if (fProjectionSupport != null) {
			fProjectionSupport.dispose();
			fProjectionSupport= null;
		}
		
		
		fMarkOccurrenceAnnotations= false;