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
return -1;
		}
		int i = 0;
		for (MMenuElement item : parentMenu.getChildren()) {
			if (id.equals(item.getElementId())) {
				return i;
			}
			i++;
		}
		return -1;
	}
	public static final String MC_POPUP = "menuContribution:popup"; 
	public static final String MC_MENU = "menuContribution:menu"; 
	public static final String MC_TOOLBAR = "menuContribution:toolbar"; 
	public static final String POPUP_PARENT_ID = "popup"; 
	public static void mergeTrimContributions(ArrayList<MTrimContribution> contributions,
			ArrayList<MTrimContribution> result) {
		HashMap<TrimKey, ArrayList<MTrimContribution>> buckets = new HashMap<TrimKey, ArrayList<MTrimContribution>>();
		trace("mergeContributions size: " + contributions.size(), null); 
		
		for (MTrimContribution contribution : contributions) {
			TrimKey key = getKey(contribution);
			ArrayList<MTrimContribution> slot = buckets.get(key);
			if (slot == null) {
				slot = new ArrayList<MTrimContribution>();
				buckets.put(key, slot);
			}
			slot.add(contribution);
		}
		Iterator<MTrimContribution> i = contributions.iterator();