Bug 92777 [Contributions] Spec clarification: ContributionItem.getParent() can return null
bundles/org.eclipse.jface/src/org/eclipse/jface/action/ContributionItem.java
this.visible = visible;
    }
    /**
     * Returns a string representation of this contribution item 
     * suitable only for debugging.
     */
    public String toString() {
        return getClass().getName() + "(id=" + getId() + ")";
    }
    /**
     * The default implementation of this <code>IContributionItem</code>
     * method does nothing. Subclasses may override.
     */
    public void update() {
    }
    /* (non-Javadoc)
     * Method declared on IContributionItem.
     */
    public void setParent(IContributionManager parent) {
        this.parent = parent;
    }
    /**
     * The <code>ContributionItem</code> implementation of this 
     * method declared on <code>IContributionItem</code> does nothing.
     * Subclasses should override to update their state.
     */
    public void update(String id) {
    }
}