Bug 127105 Package explorer hierarchical mode calls ICompilationUnit#getChildren() in PackageExplorerProblemTreeViewer#isExpandable
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
* When selection linking with the editor is enabled the view selection tracks
 * the active editor page. Similarly when a resource is selected in the packages
 * view the corresponding editor is activated. 
 */
 
public class PackageExplorerPart extends ViewPart  
	implements ISetSelectionTarget, IMenuListener,
		IShowInTarget,
		IPackagesViewPart,  IPropertyChangeListener, 
		IViewPartInputProvider {
	
	private static final String PERF_CREATE_PART_CONTROL= "org.eclipse.jdt.ui/perf/explorer/createPartControl"; 
	private static final String PERF_MAKE_ACTIONS= "org.eclipse.jdt.ui/perf/explorer/makeActions"; 
	
	private boolean fIsCurrentLayoutFlat; 
	private static final int HIERARCHICAL_LAYOUT= 0x1;
	private static final int FLAT_LAYOUT= 0x2;
	
	public final static String VIEW_ID= JavaUI.ID_PACKAGES;
				
	
	static final String TAG_SELECTION= "selection"; 
	static final String TAG_EXPANDED= "expanded"; 
	static final String TAG_ELEMENT= "element"; 
	static final String TAG_PATH= "path"; 
	static final String TAG_VERTICAL_POSITION= "verticalPosition"; 
	static final String TAG_HORIZONTAL_POSITION= "horizontalPosition"; 
	static final String TAG_FILTERS = "filters"; 
	static final String TAG_FILTER = "filter"; 
	static final String TAG_LAYOUT= "layout";