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
* Returns the working set filter for this view.
 	 * @return the working set filter
 	 */
	WorkingSetFilter getWorkingSetFilter() {
		return fWorkingSetFilter;
	}
	/**
 	 * Returns the Binary filter for this view.
 	 * @return the binary filter
 	 */
	BinaryProjectFilter getBinaryFilter() {
		return fBinaryFilter;
	}
	void restoreFilters() {
		IMemento filtersMem= fMemento.getChild(TAG_FILTERS);
		if(filtersMem != null) {	
			IMemento children[]= filtersMem.getChildren(TAG_FILTER);
			String filters[]= new String[children.length];
			for (int i = 0; i < children.length; i++) {
				filters[i]= children[i].getString(TAG_ELEMENT);
			}
			getPatternFilter().setPatterns(filters);
		} else {
			getPatternFilter().setPatterns(new String[0]);
		}
		
		String show= fMemento.getString(TAG_SHOWLIBRARIES);
		if (show != null)
			getLibraryFilter().setShowLibraries(show.equals("true")); 
		else