Bug 327765 EPartService will hide a part of another perspective
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
public int getActivated() {
			return activated;
		}
		public int getDeactivated() {
			return deactivated;
		}
		public int getHidden() {
			return hidden;
		}
		public int getVisible() {
			return visible;
		}
		public boolean isValid() {
			return valid;
		}
		public List<MPart> getActivatedParts() {
			return activatedParts;
		}
		public List<MPart> getDeactivatedParts() {
			return deactivatedParts;
		}
		public List<MPart> getHiddenParts() {
			return hiddenParts;
		}
		public List<MPart> getVisibleParts() {
			return visibleParts;
		}
		public void partActivated(MPart part) {
			if (valid && part == null) {
				valid = false;