Bug 135971 [CommonNavigator] Project Explorer: cannot drop to Hierarchy view
You can drag and drop an element onto the Hierarchy view from the Outline or Package Explorer. You cannot from the Project Explorer, you get a drop disabled cursor.
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/navigator/CommonViewer.java
* <p>
	 * Note that as of 3.2.1 and 3.3, the common viewer caches its selection.
	 * Clients must not set the selection of the viewer's tree control directly.
	 * </p>
	 * 
	 * @see org.eclipse.jface.viewers.AbstractTreeViewer#getSelection()
	 */
	public ISelection getSelection() {
		if (cachedSelection == null) {
			cachedSelection = super.getSelection();
		}
		return cachedSelection;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.jface.viewers.StructuredViewer#refresh(java.lang.Object)
	 */
	public void refresh(Object element) {
		refresh(element, true);
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.jface.viewers.StructuredViewer#update(java.lang.Object,
	 *      java.lang.String[])
	 */
	public void update(Object element, String[] properties) {
		if(element != getInput()) {
			INavigatorPipelineService pipeDream = contentService