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
private List<MPart> activatedParts = new ArrayList<MPart>();
		private List<MPart> deactivatedParts = new ArrayList<MPart>();
		private List<MPart> hiddenParts = new ArrayList<MPart>();
		private List<MPart> visibleParts = new ArrayList<MPart>();
		private int activated = 0;
		private int deactivated = 0;
		private int hidden = 0;
		private int visible = 0;
		private boolean valid = true;
		public void clear() {
			activated = 0;
			deactivated = 0;
			hidden = 0;
			visible = 0;
			activatedParts.clear();
			deactivatedParts.clear();
			hiddenParts.clear();
			visibleParts.clear();
			valid = true;
		}