Bug 318713 Duplicate toolbar items (navigate group)
SDK 4.0 - I20100701-1105. 1. start fresh workspace ==> navigate group appears twice which is quite confusing and wastes space.
bundles/org.eclipse.e4.ui.workbench/src/org/eclipse/e4/ui/internal/workbench/ContributionsAnalyzer.java
*/
		@Override
		public boolean equals(Object obj) {
			if (!(obj instanceof Key)) {
				return false;
			}
			Key other = (Key) obj;
			Object exp1 = vexp == null ? null : vexp.getCoreExpression();
			Object exp2 = other.vexp == null ? null : other.vexp.getCoreExpression();
			return Util.equals(parentId, other.parentId) && Util.equals(position, other.position)
					&& getSchemeTag() == other.getSchemeTag() && Util.equals(exp1, exp2);
		}
		@Override
		public int hashCode() {
			if (hc == -1) {
				Object exp1 = vexp == null ? null : vexp.getCoreExpression();
				hc = Util.hashCode(parentId);
				hc = hc * 87 + Util.hashCode(position);
				hc = hc * 87 + getSchemeTag();
				hc = hc * 87 + Util.hashCode(exp1);
			}
			return hc;
		}
		@Override
		public String toString() {
			return getClass().getName() + " " + parentId + "--" + position 
					+ "--" + getSchemeTag() + "--" + vexp; 
		}
	}
	static class MenuKey extends Key {