Bug 221521 [Markers] New markers API needs to be pared down
We have too much API in some of the new classes and they can be moved to internals
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/views/markers/MarkerFieldFilterGroup.java
private void initializeWorkingSet() {
		IWorkbenchWindow window = PlatformUI.getWorkbench()
				.getActiveWorkbenchWindow();
		if (window != null) {
			IWorkbenchPage page = window.getActivePage();
			if (page != null) {
				setWorkingSet(page.getAggregateWorkingSet());
				if ((PlatformUI.getPreferenceStore()
						.getBoolean(IWorkbenchPreferenceConstants.USE_WINDOW_WORKING_SET_BY_DEFAULT)))
					setScope(ON_WORKING_SET);
			}
		}
	}
	/**
	 * Return whether or not the receiver is enabled.
	 * 
	 * @return boolean
	 */
	public boolean isEnabled() {
		return enabled;
	}
	/**
	 * Return whether or not this is a system or user group.
	 * 
	 * @return boolean <code>true</code> if it is a system group.
	 */
	public boolean isSystem() {
		return element != null;
	}
	/**