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 StatusTextEditor#getStatusMessage(IStatus)
	 */
	protected String getStatusMessage(IStatus status) {
		if (fEncodingSupport != null) {
			String message= fEncodingSupport.getStatusMessage(status);
			if (message != null)
				return message;
		}
		return super.getStatusMessage(status);
	}
	
	/*
	 * @see AbstractTextEditor#doSetInput
	 */
	protected void doSetInput(IEditorInput input) throws CoreException {
		ISourceViewer sourceViewer= getSourceViewer();
		if (!(sourceViewer instanceof ISourceViewerExtension2)) {
			setPreferenceStore(createCombinedPreferenceStore(input));
			internalDoSetInput(input);
			return;
		}
		
		getSourceViewerDecorationSupport(sourceViewer).uninstall();
		((ISourceViewerExtension2)sourceViewer).unconfigure();
		
		setPreferenceStore(createCombinedPreferenceStore(input));
		
		 
		sourceViewer.configure(getSourceViewerConfiguration());
		getSourceViewerDecorationSupport(sourceViewer).install(getPreferenceStore());