Bug 327765 EPartService will hide a part of another perspective
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/PartActivationHistory.java
return null;
	}
	private MPart getActivationCandidate(LinkedList<MPart> activationHistory, MPart part) {
		MArea area = isInArea(part);
		if (area != null) {
			
			MPart candidate = getSiblingActivationCandidate(part);
			if (candidate != null) {
				return candidate;
			}
			
			for (MPart element : modelService.findElements(area, null, MPart.class, null)) {
				if (element != part) {
					if (element.isToBeRendered() && element.isVisible()) {
						MPlaceholder placeholder = element.getCurSharedRef();
						if (placeholder == null
								|| (placeholder.isToBeRendered() && placeholder.isVisible())) {
							return element;
						}
					}
				}
			}
		}
		for (Iterator<MPart> it = activationHistory.iterator(); it.hasNext();) {
			if (it.next() == part) {
				if (part == activationHistory.getFirst() && it.hasNext()) {
					MPart candidate = it.next();
					if (candidate.isToBeRendered() && candidate.isVisible()) {
						MPlaceholder placeholder = candidate.getCurSharedRef();
						if (placeholder == null