Deadlock-prone locking changes in Introspector

Locking model of Introspector changed by fix of
bug 5102804. The code

(new Introspector(beanClass, null, USE_ALL_BEANINFO)).getBeanInfo();

is called under BEANINFO_CACHE lock by now, see getBeanInfo(Class) method.
This code can invoke 3rd-party code through findExplicitBeanInfo().
It is deadlock-prone to call 3rd-party code under some lock
and it should be avoided where it is possible.

See the following test-case. It shows how easily the mentioned
changes can result in a deadlock.

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package problemofintrospector;

import java.awt.Point;
import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.SimpleBeanInfo;

public class TestCase {

    public static void main(String[] args) throws Exception {
        Thread t1 = new Thread(new Runnable() {
            public void run() {
                try {
                    // Get some BeanInfo in one thread
                    Introspector.getBeanInfo(CustomizedPoint.class, Object.class);
                } catch (IntrospectionException iex) {}
            }
        });
        Thread t2 = new Thread(new Runnable() {
            public void run() {
                try {
                    // Get some BeanInfo in another thread
                    Introspector.getBeanInfo(Point.class);
                } catch (IntrospectionException iex) {}
            }
        });
        t1.start();
        Thread.sleep(500); // increase the chance of the deadlock
        t2.start();
    }

    public static class CustomizedPoint extends Point {
    }

    public static class CustomizedPointBeanInfo extends SimpleBeanInfo {
        private BeanInfo superInfo;

        public CustomizedPointBeanInfo() {
            try {
                Thread.sleep(1000); // increase the chance of the deadlock
                superInfo = Introspector.getBeanInfo(Point.class);
            } catch (Exception ex) {
                ex.printStackTrace();
            }
        }

        // Real-life BeanInfo would contain some additional
        // methods overriden and some work delegated to superInfo
        // (the corresponding code is skipped because it is not
        // necessary to reproduce the deadlock).

    }

}

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Note that the test-case doesn't run into deadlock on older JDK builds
(pre JDK 6 update 21 build 02), i.e., it is a regression. Also note
that this test-case is not an artifical one. It is based on a deadlock
that one of our users faces regularly while using NetBeans GUI Builder.