Bug 326087 StackRenderer arbitrarily changes selected element when MPartStack is being unrendered
1. Open two files. 2. Activate the editor in the back. 3. Restart 4. The file in the wrong is active now. :O
bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/StackRenderer.java
for (MUIElement mPart : stack.getChildren()) {
			if (mPart == part)
				return index;
			if (mPart.isToBeRendered())
				index++;
		}
		return index;
	}
	@Override
	public void childRendered(
			final MElementContainer<MUIElement> parentElement,
			MUIElement element) {
		super.childRendered(parentElement, element);
		if (!(((MUIElement) parentElement) instanceof MPartStack)
				|| !(element instanceof MStackElement))
			return;
		createTab(parentElement, element);
	}
	private CTabItem findItemForPart(MUIElement element,
			MElementContainer<MUIElement> stack) {
		if (stack == null)
			stack = element.getParent();
		CTabFolder ctf = (CTabFolder) stack.getWidget();
		if (ctf == null)
			return null;
		CTabItem[] items = ctf.getItems();
		for (int i = 0; i < items.length; i++) {
			if (items[i].getData(OWNING_ME) == element)
				return items[i];
		}