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
* Returns the Device for which this ResourceManager will create resources 
     * 
     * @since 3.1
     *
     * @return the Device associated with this ResourceManager
     */
    public abstract Device getDevice();
    
    /**
     * Returns the resource described by the given descriptor. If the resource already
     * exists, the reference count is incremented and the exiting resource is returned.
     * Otherwise, a new resource is allocated. Every call to this method must have
     * a corresponding call to {@link #destroy(DeviceResourceDescriptor)}, or 
     * an eventual call to {@link #dispose()}.
     * 
     * @since 3.1 
     *
     * @param descriptor descriptor for the resource to allocate
     * @return the newly allocated resource (not null)
     * @throws DeviceResourceException if unable to allocate the resource
     */
    public abstract Object create(DeviceResourceDescriptor descriptor) throws DeviceResourceException;
    
    /**
     * Deallocates a resource previously allocated by {@link #create(DeviceResourceDescriptor)}. 
     * Descriptors are compared by equality, not identity. If the same resource was 
     * created multiple times, this may decrement a reference count rather than 
     * disposing the actual resource.  
     * 
     * @since 3.1