Bug 339573 Splitting the shared area with a part doesn't remove stale placeholders
The current code only looks for the addition of an MPlaceholder in the shared area as the hint to remove locals. When you split the area the element that gets added is the new MPartSashContainer...
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/ModelServiceImpl.java
* @see org.eclipse.e4.ui.workbench.modeling.EModelService#find(java.lang.String,
	 * org.eclipse.e4.ui.model.application.MElementContainer)
	 */
	public MUIElement find(String id, MUIElement searchRoot) {
		if (id == null || id.length() == 0)
			return null;
		List elements = findElements(searchRoot, id, null, null);
		if (elements.size() > 0)
			return (MUIElement) elements.get(0);
		return null;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see
	 * org.eclipse.e4.ui.workbench.modeling.EModelService#getContainingContext(org.eclipse.e4.ui
	 * .model .application.MUIElement)
	 */
	public IEclipseContext getContainingContext(MUIElement element) {
		return ModelUtils.getContainingContext(element);
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see
	 * org.eclipse.e4.ui.workbench.modeling.EModelService#bringToTop(org.eclipse.e4.ui.model.application
	 * .ui.MUIElement)
	 */
	public void bringToTop(MUIElement element) {
		if (element instanceof MApplication)