Bug 314685 EModelService's findElements(MUIElement, String, Class<T>, List<String>) method can return duplicates
I'm getting two editors in the returned list that's pointing at the same thing. The returned collection is a List and not a Set but this feels wrong.
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/workbench/ui/internal/ModelServiceImpl.java
public void bringToTop(MWindow window, MUIElement element) {
		if (element instanceof MApplication)
			return;
		MUIElement parent = element.getParent();
		if (parent == null) {
			MPlaceholder ph = findPlaceholderFor(window, element);
			if (ph != null) {
				element = ph;
				parent = element.getParent();
			}
		}
		if (parent != null) {
			
			if (!element.isToBeRendered())
				element.setToBeRendered(true);
			((MElementContainer<MUIElement>) parent).setSelectedElement(element);
			bringToTop(window, parent);
		}
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see
	 * org.eclipse.e4.workbench.modeling.EModelService#findPlaceholderFor(org.eclipse.e4.ui.model
	 * .application.ui.basic.MWindow, org.eclipse.e4.ui.model.application.ui.MUIElement)
	 */
	public MPlaceholder findPlaceholderFor(MWindow window, MUIElement element) {
		List<MPerspectiveStack> psList = findElements(window, null, MPerspectiveStack.class, null);
		if (psList.size() != 1)
			return null;