Bug 150593 Enhancements for ResourceManager
The attached patch addresses the following in ResourceManager - Fixes several JavaDoc bugs - Adds a "getImage" method that implements the common pattern of "return existing image if known, or allocate a new image otherwise"
bundles/org.eclipse.jface/src/org/eclipse/jface/resource/ResourceManager.java
return (Color)create(descriptor);
    }
    /**
     * Allocates a color, given its RGB value. Any color allocated in this
     * manner must be disposed by calling {@link #destroyColor(RGB)}, 
     * or by an eventual call to {@link #dispose()}. {@link Color#dispose()} must
     * never been called directly on the returned color.
     * 
     * @since 3.1 
     *
     * @param descriptor descriptor for the color to create
     * @return the Color described by the given ColorDescriptor (not null)
     * @throws DeviceResourceException if unable to create the color
     */
    public final Color createColor(RGB descriptor) throws DeviceResourceException {
        return createColor(new RGBColorDescriptor(descriptor));
    }
    
    /**
     * Undoes everything that was done by a call to {@link #createColor(RGB)}.
     * 
     * @since 3.1 
     *
     * @param descriptor RGB value of the color to dispose
     */
    public final void destroyColor(RGB descriptor) {
        destroyColor(new RGBColorDescriptor(descriptor));
    }
    /**
     * Undoes everything that was done by a call to {@link #createColor(ColorDescriptor)}.