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
for (int c = 0; c < array.length; c++) {
					MToolBarElement me = (MToolBarElement) array[c];
					if (!containsMatching(toContribute.getChildren(), me)) {
						toContribute.getChildren().add(me);
					}
				}
			}
			if (toContribute != null) {
				toContribute.setWidget(null);
				result.add(toContribute);
			}
		}
		trace("mergeContributions: final size: " + result.size(), null); 
	}
	public static void mergeContributions(ArrayList<MMenuContribution> contributions,
			ArrayList<MMenuContribution> result) {
		HashMap<MenuKey, ArrayList<MMenuContribution>> buckets = new HashMap<MenuKey, ArrayList<MMenuContribution>>();
		trace("mergeContributions size: " + contributions.size(), null); 
		printContributions(contributions);
		
		for (MMenuContribution contribution : contributions) {
			MenuKey key = getKey(contribution);
			ArrayList<MMenuContribution> slot = buckets.get(key);
			if (slot == null) {
				slot = new ArrayList<MMenuContribution>();
				buckets.put(key, slot);
			}
			slot.add(contribution);
		}
		Iterator<MMenuContribution> i = contributions.iterator();