Bug 123424 browsing perspective does not show some packages in hierarchical mode
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/browsing/PackagesView.java
*
	 * @return	the string used as ID for the Help context
	 */
	protected String getHelpContextId() {
		return IJavaHelpContextIds.PACKAGES_BROWSING_VIEW;
	}
	protected String getLinkToEditorKey() {
		return PreferenceConstants.LINK_BROWSING_PACKAGES_TO_EDITOR;
	}
	/**
	 * Answers if the given <code>element</code> is a valid
	 * input for this part.
	 *
	 * @param 	element	the object to test
	 * @return	<true> if the given element is a valid input
	 */
	protected boolean isValidInput(Object element) {
		if (element instanceof IJavaProject || (element instanceof IPackageFragmentRoot && ((IJavaElement)element).getElementName() != IPackageFragmentRoot.DEFAULT_PACKAGEROOT_PATH))
			try {
				IJavaProject jProject= ((IJavaElement)element).getJavaProject();
				if (jProject != null)
					return jProject.getProject().hasNature(JavaCore.NATURE_ID);
			} catch (CoreException ex) {
				return false;
			}
		return false;
	}
	/**
	 * Answers if the given <code>element</code> is a valid
	 * element for this part.