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
return (Color) result;
        Color color = null;
        result = stringToRGB.get(symbolicName);
        if (result == null)
            return null;
        color = createColor(symbolicName, (RGB) result);
        stringToColor.put(symbolicName, color);
        return color;
    }
    /* (non-Javadoc)
     * @see org.eclipse.jface.resource.ResourceRegistry#getKeySet()
     */
    public Set getKeySet() {
        return Collections.unmodifiableSet(stringToRGB.keySet());
    }
    /**
     * Returns the color data associated with the given symbolic color name.
     *
     * @param symbolicName symbolic color name.
     * @return the <code>RGB</code> data.
     */
    public RGB getRGB(String symbolicName) {
        Assert.isNotNull(symbolicName);
        return (RGB) stringToRGB.get(symbolicName);
    }
    /* (non-Javadoc)
     * @see org.eclipse.jface.resource.ResourceRegistry#clearCaches()
     */
    protected void clearCaches() {
        disposeColors(stringToColor.values().iterator());