Bug 25827 Disposing of MemberFilterActionGroup
Build 2.0.2 and 2.1 When investigating an editor memory leak PR we found out that this group has a dispose method which is never called. When we then called from the editor it throw an exeption (viewer was disposed). Don't know if the group really needs dispose() if so it should get called.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/typehierarchy/TypeHierarchyViewPart.java
*/
	private void setViewerVisibility(boolean showHierarchy) {
		if (showHierarchy) {
			fViewerbook.showPage(getCurrentViewer().getControl());
		} else {
			fViewerbook.showPage(fEmptyTypesViewer);
		}
	}
	
	/**
	 * Sets the member filter. <code>null</code> disables member filtering.
	 */	
	private void setMemberFilter(IMember[] memberFilter) {
		Assert.isNotNull(fAllViewers);
		for (int i= 0; i < fAllViewers.length; i++) {
			fAllViewers[i].setMemberFilter(memberFilter);
		}
	}	
	
	private IType getSelectableType(IJavaElement elem) {
		if (elem.getElementType() != IJavaElement.TYPE) {
			return null; 
		} else {
			return (IType) elem;
		}
	}
	
	private void internalSelectType(IMember elem, boolean reveal) {	
		TypeHierarchyViewer viewer= getCurrentViewer();
		viewer.removeSelectionChangedListener(fSelectionChangedListener);