Bug 259179 [TabbedProperties] TabbedPropertySheetPage extensibility option
bundles/org.eclipse.ui.views.properties.tabbed/src/org/eclipse/ui/views/properties/tabbed/TabbedPropertySheetPage.java
if (newContributor == null) {
			/**
			 * selection does not implement or adapt ITabbedPropertySheetPageContributor.
			 */
			newContributor = contributor;
		}
		
        String selectionContributorId = newContributor.getContributorId();
		if (selectionContributorId.equals(currentContributorId)) {
			/**
			 * selection has the same contributor id as current, so leave
			 * existing registry.
			 */
			return;
		}
		/**
		 * Selection implements ITabbedPropertySheetPageContributor different
		 * than current contributor id, so make sure all elements implement the
		 * new id. If all contributor id do not match, then fall back to default
		 * contributor from the workbench part.
		 */
		Iterator i = structuredSelection.iterator();
        i.next();
		while (i.hasNext()) {
            newContributor = getTabbedPropertySheetPageContributor(i.next());
			if (newContributor == null || !newContributor.getContributorId().equals(selectionContributorId)) {
				/**
				 * fall back to use the default contributor id from the
				 * workbench part.
				 */