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 (ToolBarKey) contribution.getWidget();
		}
		return new ToolBarKey(contribution);
	}
	private static TrimKey getKey(MTrimContribution contribution) {
		if (contribution.getWidget() instanceof TrimKey) {
			return (TrimKey) contribution.getWidget();
		}
		return new TrimKey(contribution);
	}
	public static void printContributions(ArrayList<MMenuContribution> contributions) {
		for (MMenuContribution c : contributions) {
			trace("\n" + c, null); 
			for (MMenuElement element : c.getChildren()) {
				printElement(1, element);
			}
		}
	}
	private static void printElement(int level, MMenuElement element) {
		StringBuilder buf = new StringBuilder();
		for (int i = 0; i < level; i++) {
			buf.append('\t');
		}
		buf.append(element.toString());
		trace(buf.toString(), null);
		if (element instanceof MMenu) {
			for (MMenuElement item : ((MMenu) element).getChildren()) {
				printElement(level + 1, item);
			}
		}