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
}
		if (!isActivePart() && JavaPlugin.getActivePage() != null)
			JavaPlugin.getActivePage().bringToTop(this);
			
		setSelection(reference, !isActivePart());
	}
	
	/*
	 * @see AbstractTextEditor#adjustHighlightRange(int, int)
	 */
	protected void adjustHighlightRange(int offset, int length) {
		
		try {
			
			IJavaElement element= getElementAt(offset);
			while (element instanceof ISourceReference) {
				ISourceRange range= ((ISourceReference) element).getSourceRange();
				if (offset < range.getOffset() + range.getLength() && range.getOffset() < offset + length) {
					
					ISourceViewer viewer= getSourceViewer();
					if (viewer instanceof ITextViewerExtension5) {
						ITextViewerExtension5 extension= (ITextViewerExtension5) viewer;
						extension.exposeModelRange(new Region(range.getOffset(), range.getLength()));
					}
					
					setHighlightRange(range.getOffset(), range.getLength(), true);
					if (fOutlinePage != null) {
						fOutlineSelectionChangedListener.uninstall(fOutlinePage);
						fOutlinePage.select((ISourceReference) element);
						fOutlineSelectionChangedListener.install(fOutlinePage);