Bug 11748 switch to new DecoratorManager API
From the workbench change notes: API changes IWorkbenchPartSite.getDecoratorManager() - As the DecoratorManager has proven to be required for more than just IWorkbenchPartSites we have moved getDecoratorManager() to IWorkbench and deprecated the getDecoratorManager() in IWorkbenchPartSite. The one in IWorkbenchPartSite will be removed after the other Eclipse components have had a chance to switch to the new API.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
* Saves the state of the filter actions
	 */
	public void saveMemberFilterState(IMemento memento) {
		fMemberFilterActionGroup.saveState(memento);
	}
	void restoreState(IMemento memento) {
		restoreExpansionState(memento);
		restoreSelectionState(memento);
		restoreScrollState(memento, fViewer.getTree());
	}
	protected void restoreScrollState(IMemento memento, Tree tree) {
		ScrollBar bar= tree.getVerticalBar();
		if (bar != null) {
			try {
				String posStr= memento.getString(TAG_VERTICAL_POSITION);
				int position;
				position= new Integer(posStr).intValue();
				bar.setSelection(position);
			} catch (NumberFormatException e) {
				
			}
		}
		bar= tree.getHorizontalBar();
		if (bar != null) {
			try {
				String posStr= memento.getString(TAG_HORIZONTAL_POSITION);
				int position;
				position= new Integer(posStr).intValue();
				bar.setSelection(position);
			} catch (NumberFormatException e) {