Bug 328946 Part activation history may return incorrect candidate if no placeholders could be found in a perspective
1. Window > Open Perspective > Other... > CVS Repository Exploring 2. Hide the 'CVS Repositories' view. 3. The 'History' view should become active, it is not.
tests/org.eclipse.e4.ui.tests/src/org/eclipse/e4/ui/tests/application/EPartServiceTest.java
}
			activated++;
			activatedParts.add(part);
		}
		public void partBroughtToTop(MPart part) {
		}
		public void partDeactivated(MPart part) {
			if (valid && part == null) {
				valid = false;
			}
			deactivated++;
			deactivatedParts.add(part);
		}
		public void partHidden(MPart part) {
			if (valid && part == null) {
				valid = false;
			}
			hidden++;
			hiddenParts.add(part);
		}
		public void partVisible(MPart part) {
			if (valid && part == null) {
				valid = false;
			}
			visible++;
			visibleParts.add(part);
		}
	}
}