protected Class<?> delegateToParent(String classname)
            throws ClassNotFoundException {
        ClassLoader cl = getParent();
        if (cl != null) {
            return cl.loadClass(classname);
        } else {
            return findSystemClass(classname);
        }
    }
Finds the specified class using <code>ClassPath</code>.
If the source throws an exception, this returns null.
<p>
<p>This method can be overridden by a subclass of
<code>Loader</code>.  Note that the overridden method must not throw
an exception when it just fails to find a class file.

@return null if the specified class could not be found.
@throws ClassNotFoundException if an exception is thrown while
                               obtaining a class file.
agent-module/profiler-test/src/main/java/com/navercorp/pinpoint/profiler/test/classloader/TransformClassLoader.java