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
* (key type: <code>String</code>, 
     *  value type: <code>FontRecord</code>.
     */
    private Map stringToFontRecord = new HashMap(7);
    /**
     * Table of known font data, keyed by symbolic font name
     * (key type: <code>String</code>, 
     *  value type: <code>org.eclipse.swt.graphics.FontData[]</code>).
     */
    private Map stringToFontData = new HashMap(7);
    /**
     * Collection of Fonts that are now stale to be disposed
     * when it is safe to do so (i.e. on shutdown).
     * @see List
     */
    private List staleFonts = new ArrayList();
    /**
     * Runnable that cleans up the manager on disposal of the display.
     */
    protected Runnable displayRunnable = new Runnable() {
        public void run() {
            clearCaches();
        }
    };
    /**
     * Creates an empty font registry.
     * <p>
     * There must be an SWT Display created in the current 
     * thread before calling this method.
     * </p>