Bug 187796 [KeyBindings] IBindingService cannot return best active bindings for a ParameterizedCommand
IBindingService only supports getBestActiveBindingFor(final String commandId) ... there must be an equivalent method for ParameterizedCommands PW
bundles/org.eclipse.jface/src/org/eclipse/jface/bindings/BindingManager.java
* @return The tree of contexts to use; may be empty, but never
	 *         <code>null</code>. The keys and values are both strings.
	 */
	private final Map createContextTreeFor(final Set contextIds) {
		final Map contextTree = new HashMap();
		final Iterator contextIdItr = contextIds.iterator();
		while (contextIdItr.hasNext()) {
			String childContextId = (String) contextIdItr.next();
			while (childContextId != null) {
				
				if (contextTree.containsKey(childContextId)) {
					break;
				}
				
				final Context childContext = contextManager
						.getContext(childContextId);
				
				try {
					final String parentContextId = childContext.getParentId();
					contextTree.put(childContextId, parentContextId);
					childContextId = parentContextId;
				} catch (final NotDefinedException e) {
					break; 
				}
			}
		}
		return contextTree;
	}
	/**
	 * <p>