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
|| (placeholder.isToBeRendered() && placeholder.isVisible())) {
							return candidate;
						}
					}
				}
				return getActivationCandidate(part);
			}
		}
		return getActivationCandidate(part);
	}
	public MPart getNextActivationCandidate(MPart part) {
		LinkedList<MPart> activationHistory = getPerspectiveActivationHistory(part);
		return getActivationCandidate(activationHistory == null ? generalActivationHistory
				: activationHistory, part);
	}
	public void forget(MPart part, boolean full) {
		generalActivationHistory.remove(part);
		if (full) {
			for (LinkedList<MPart> history : perspectiveActivationHistories.values()) {
				history.remove(part);
			}
		} else {
			LinkedList<MPart> history = getPerspectiveActivationHistory(part);
			if (history != null) {
				history.remove(part);
			}
		}
	}
	MPart getActivationCandidate(MPerspective perspective) {
		Collection<MPart> candidates = perspectiveActivationHistories.get(perspective);