Bug 322356 EPS's isPartVisible(MPart) method does not consider placeholders
SSIA
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/PartServiceImpl.java
* (non-Javadoc)
	 * 
	 * @see org.eclipse.e4.ui.workbench.modeling.EPartService#getActivePart()
	 */
	public MPart getActivePart() {
		return activePart;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see
	 * org.eclipse.e4.ui.workbench.modeling.EPartService#deactivate(org.eclipse.e4.ui.model.application
	 * .MPart)
	 */
	public void deactivate(MPart part) {
		MElementContainer<MUIElement> parent = part.getParent();
		MPart oldSelectedElement = (MPart) parent.getSelectedElement();
		if (oldSelectedElement == part) {
			parent.setSelectedElement(null);
			internalFixContext(null, oldSelectedElement);
		}
	}
	private MPartDescriptor findDescriptor(String id) {
		for (MPartDescriptor descriptor : application.getDescriptors()) {
			if (descriptor.getElementId().equals(id)) {
				return descriptor;
			}
		}
		return null;
	}