Change to ProgressSource in JDK 7 causes NoSuchMethodError in new Java Plug-in

If the new Java Plug-In is run and a JDK 7 build is named in deployment.properties, applets will fail to load with the following exception:

java.lang.NoSuchMethodError: sun.net.ProgressSource.getProgress()I
at sun.plugin.util.ProgressMonitor.registerSource(ProgressMonitor.java:129)
at sun.net.ProgressSource.beginTracking(ProgressSource.java:148)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1031)
at java.net.HttpURLConnection.getResponseCode(HttpURLConnection.java:397)
at sun.plugin2.applet.Applet2ClassLoader.getBytes(Applet2ClassLoader.java:361)
at sun.plugin2.applet.Applet2ClassLoader.access$100(Applet2ClassLoader.java:47)
at sun.plugin2.applet.Applet2ClassLoader$1.run(Applet2ClassLoader.java:153)
at java.security.AccessController.doPrivileged(Native Method)
at sun.plugin2.applet.Applet2ClassLoader.findClass(Applet2ClassLoader.java:150)
at java.lang.ClassLoader.loadClass(ClassLoader.java:324)
at java.lang.ClassLoader.loadClass(ClassLoader.java:269)
at sun.plugin2.applet.Applet2ClassLoader.loadCode(Applet2ClassLoader.java:695)
at sun.plugin2.applet.Applet2Manager.createApplet(Applet2Manager.java:2246)
at sun.plugin2.applet.Applet2Manager.access$1500(Applet2Manager.java:83)
at sun.plugin2.applet.Applet2Manager$AppletExecutionRunnable.run(Applet2Manager.java:845)
at java.lang.Thread.run(Thread.java:675)

This is happening because ProgressSource.getProgress() was changed to return a long instead of an int in JDK 7 in 5052093. Since the new plug-in needs to run on multiple JRE versions, we need to change the code in sun.plugin.util.ProgressMonitor() to call ProgressSource.getProgress() and the ProgressEvent constructor reflectively, or find another solution.