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/typehierarchy/TypeHierarchyViewer.java
/**
	 * Returns true if the hierarchy contains element the element.
	 */ 
	public boolean isElementShown(Object element) {
		return findItem(element) != null;
	}
	
	/**
	 * Updates the content of this viewer: refresh and expanding the tree in the way wanted.
	 */
	public abstract void updateContent();	
	
	/**
	 * Returns the title for the current view
	 */
	public abstract String getTitle();
	
	/*
	 * @see StructuredViewer#setContentProvider
	 * Content provider must be of type TypeHierarchyContentProvider
	 */
	public void setContentProvider(IContentProvider cp) {
		Assert.isTrue(cp instanceof TypeHierarchyContentProvider);
		super.setContentProvider(cp);
	}
	protected TypeHierarchyContentProvider getHierarchyContentProvider() {
		return (TypeHierarchyContentProvider)getContentProvider();
	}
	
}