Bug 65187 [Themes] Cascading*Registry leakage from Colors and Fonts pref page
Small leak on I20040529 For each ColorsAndFontsPreferencePage this is created, the cascading font and color registries are leaked. This is because the superclasses register a runnable with Display#disposeExec
bundles/org.eclipse.jface/src/org/eclipse/jface/resource/ColorRegistry.java
* 
     * @param symbolicName the symbolic color name.
     * @param rgb the <code>RGB</code> data for the color.
     * @return the new <code>Color</code> object.
     */
    private Color createColor(String symbolicName, RGB rgb) {
        return new Color(display, rgb);
    }
    /**
     * Dispose of all of the <code>Color</code>s in this iterator.
     * 
     * @param Iterator over <code>Collection</code> of <code>Color</code>
     */
    private void disposeColors(Iterator iterator) {
        while (iterator.hasNext()) {
            Object next = iterator.next();
            ((Color) next).dispose();
        }
    }
    /**
     * Returns the <code>color</code> associated with the given symbolic color 
     * name, or <code>null</code> if no such definition exists.
     * 
     * @param symbolicName symbolic color name
     * @return the <code>Color</code> or <code>null</code>
     */
    public Color get(String symbolicName) {
        Assert.isNotNull(symbolicName);
        Object result = stringToColor.get(symbolicName);
        if (result != null)