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
/*
	 *  (non-Javadoc)
	 * @see org.eclipse.jface.viewers.Viewer#setSelection(org.eclipse.jface.viewers.ISelection, boolean)
	 */
	public void setSelection(ISelection selection, boolean reveal) { 
		if(selection instanceof IStructuredSelection) {
			IStructuredSelection sSelection = (IStructuredSelection) selection;
			
			INavigatorPipelineService pipeDream = contentService
					.getPipelineService();
			PipelinedViewerUpdate update = new PipelinedViewerUpdate();
			update.getRefreshTargets().addAll(sSelection.toList());
			update.setUpdateLabels(false);
			
			if (pipeDream.interceptRefresh(update)) {
				 
				super.setSelection(new StructuredSelection(update.getRefreshTargets().toArray()) , reveal);
			} else {
				super.setSelection(selection, reveal);
			}
		}
	}
	
    /* (non-Javadoc)
     * @see org.eclipse.jface.viewers.ContentViewer#hookControl(Control)
     */
    protected void hookControl(Control control) {
    	super.hookControl(control);