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
} else {
				MUIElement parentCandidate = parent.getParent();
				if (parentCandidate == null) {
					placeholder = parent.getCurSharedRef();
					if (placeholder == null) {
						return null;
					}
					parentCandidate = placeholder.getParent();
					if (parentCandidate == null) {
						return null;
					}
				}
				parent = parentCandidate;
			}
		}
		return null;
	}
	Object getSiblingActivationCandidate2() {
		Object history = perspectiveActivationHistories.get(null);
		if (history == null) {
			return null;
		}
		return history == null ? null : null;
	}
	private MPart getSiblingActivationCandidate(MPart part, MUIElement element) {
		MUIElement parent = element.getParent();
		while (parent != null) {
			if (parent instanceof MPerspective) {
				LinkedList<MPart> history = perspectiveActivationHistories.get(parent);
				return history == null ? null : getSiblingActivationCandidate(part, element,