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/DeviceResourceException.java
*/
    public DeviceResourceException(DeviceResourceDescriptor missingResource, Throwable cause) {
        super("Unable to create resource " + missingResource.toString()); 
        
        this.cause = cause;
    }
    
    /**
     * Creates a DeviceResourceException indicating an error attempting to
     * create a resource 
     * 
     * @param missingResource
     */
    public DeviceResourceException(DeviceResourceDescriptor missingResource) {
        this(missingResource, null);
    }
    
    /**
     * Returns the cause of this throwable or <code>null</code> if the
     * cause is nonexistent or unknown. 
     * 
     * @return the cause or <code>null</code>
     * @since 3.1
     */
    public Throwable getCause() {
        return cause;
    }
    
}