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/FontRegistry.java
* @param symbolicName the symbolic font name
     * @param fontData an Array of FontData
     * @param update - fire a font mapping changed if true. False
     * 	if this method is called from the get method as no setting
     *  has changed.
     */
    private void put(String symbolicName, FontData[] fontData, boolean update) {
        Assert.isNotNull(symbolicName);
        Assert.isNotNull(fontData);
        FontData[] existing = (FontData[]) stringToFontData.get(symbolicName);
        if (Arrays.equals(existing, fontData))
            return;
        FontRecord oldFont = (FontRecord) stringToFontRecord
                .remove(symbolicName);
        stringToFontData.put(symbolicName, fontData);
        if (update)
            fireMappingChanged(symbolicName, existing, fontData);
        if (oldFont != null)
            oldFont.addAllocatedFontsToStale(defaultFontRecord().getBaseFont());
    }
    /**
     * Reads the resource bundle.  This puts FontData[] objects
     * in the mapping table.  These will lazily be turned into
     * real Font objects when requested.
     */
    private void readResourceBundle(ResourceBundle bundle, String bundleName)
            throws MissingResourceException {
        Enumeration keys = bundle.getKeys();
        while (keys.hasMoreElements()) {
            String key = (String) keys.nextElement();