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
MWindow win = modelService
						.getTopLevelWindowFor(stackToActivate);
				MPerspective activePersp = modelService
						.getActivePerspective(win);
				MPerspective myPersp = modelService
						.getPerspectiveFor(stackToActivate);
				if (activePersp != null && myPersp != activePersp)
					return;
				MUIElement selElement = stackToActivate.getSelectedElement();
				if (!selElement.isToBeRendered())
					return;
				if (selElement instanceof MPlaceholder)
					selElement = ((MPlaceholder) selElement).getRef();
				activate((MPart) selElement);
			}
		}
	}
	private ActivationJob activationJob = null;
	synchronized private void activateStack(MElementContainer<MUIElement> stack) {
		CTabFolder ctf = (CTabFolder) stack.getWidget();
		if (ctf == null || ctf.isDisposed())
			return;
		if (activationJob == null) {
			activationJob = new ActivationJob();
			activationJob.stackToActivate = stack;
			ctf.getDisplay().asyncExec(activationJob);
		} else {
			activationJob.stackToActivate = stack;
		}