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
disposeColors(staleColors.iterator());
        stringToColor.clear();
        staleColors.clear();
    }
    /* (non-Javadoc)
     * @see org.eclipse.jface.resource.ResourceRegistry#hasValueFor(java.lang.String)
     */
    public boolean hasValueFor(String colorKey) {
        return stringToRGB.containsKey(colorKey);
    }
    /**
     * Hook a dispose listener on the SWT display.
     */
    private void hookDisplayDispose() {
        display.disposeExec(displayRunnable);
    }
    /**
     * Adds (or replaces) a color to this color registry under the given 
     * symbolic name.
     * <p>
     * A property change event is reported whenever the mapping from a symbolic
     * name to a color changes. The source of the event is this registry; the
     * property name is the symbolic color name.
     * </p>
     * 
     * @param symbolicName the symbolic color name
     * @param colorData an <code>RGB</code> object
     */
    public void put(String symbolicName, RGB colorData) {
        put(symbolicName, colorData, true);