FULL PRODUCT VERSION :
java version "1.8.0"
Java(TM) SE Runtime Environment (build 1.8.0-b132)
Java HotSpot(TM) 64-Bit Server VM (build 25.0-b70, mixed mode)

java version "1.8.0"
Java(TM) SE Runtime Environment (build 1.8.0-b132)
Java HotSpot(TM) Client VM (build 25.0-b70, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

EXTRA RELEVANT SYSTEM CONFIGURATION :
No direct connection to the internet - only via http/socks-proxys

A DESCRIPTION OF THE PROBLEM :
The JavaScript engine Nashorn is unable to evaluate an autoproxy configuration when in deployment.properties deployment.proxy.auto.config.url is used and the autoconfig script contains any function that calls dnsResolve.

Common part of Exception is always
Caused by: <eval>:34 TypeError: com.sun.deploy.net.proxy.SunAutoProxyHandler@........ has no such function "dnsResolve"
.
.
.
	at jdk.nashorn.internal.scripts.Script$\^eval\_.dnsResolve(<eval>:34)
.
.
.
	at jdk.nashorn.internal.scripts.Script$\^eval\_.FindProxyForURL(<eval>:188)
	at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:502)

REGRESSION.  Last worked in version 7u51

ADDITIONAL REGRESSION INFORMATION: 
java version "1.8.0"
Java(TM) SE Runtime Environment (build 1.8.0-b132)
Java HotSpot(TM) 64-Bit Server VM (build 25.0-b70, mixed mode)

java version "1.8.0"
Java(TM) SE Runtime Environment (build 1.8.0-b132)
Java HotSpot(TM) Client VM (build 25.0-b70, mixed mode)

Also fails in jdk8 b128. Haven't tested older jdk8 builds.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Deploy an autoconfig.conf like this:
====================
function FindProxyForURL(url, host)
{
	if(dnsResolve(host) == '') {
		return "DIRECT"
	}
	if (isResolvable(host) && false)
	{
		return "DIRECT";
	}
	if (isInNet(host, "255.255.0.0", "255.255.0.0") && false)
	{
		return "DIRECT";
	}
	return "PROXY yourproxy:yourproxyport";
}
====================

2. Compile the following to a .class and place it in a signed jar along with an APPLICATION.jnlp etc.

Testclass:
====================
see below <Source code for an executable test case>
====================

3. Run your webstart-app

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
When executing url_.openConnection().getInputStream()
Nashorn should evaluate the autoconfig and select the right proxy.
ACTUAL -
Nashorn throws an exception whenever dnsResolve, isResolvable or isInNet is called. Other functions that in turn call dnsResolve may be affected, too.
No proxy is used then and the connection fails.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
javax.script.ScriptException: TypeError: com.sun.deploy.net.proxy.SunAutoProxyHandler@74a3b2dc has no such function "dnsResolve" in <eval> at line number 34
	at jdk.nashorn.api.scripting.NashornScriptEngine.throwAsScriptException(NashornScriptEngine.java:564)
	at jdk.nashorn.api.scripting.NashornScriptEngine.invokeImpl(NashornScriptEngine.java:514)
	at jdk.nashorn.api.scripting.NashornScriptEngine.invokeFunction(NashornScriptEngine.java:229)
	at com.sun.deploy.net.proxy.SunAutoProxyHandler.getProxyInfo(Unknown Source)
	at com.sun.deploy.net.proxy.DynamicProxyManager.getProxyList(Unknown Source)
	at com.sun.deploy.net.proxy.DeployProxySelector.select(Unknown Source)
	at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(Unknown Source)
	at sun.net.www.protocol.http.HttpURLConnection$6.run(Unknown Source)
	at sun.net.www.protocol.http.HttpURLConnection$6.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.AccessController.doPrivileged(Unknown Source)
	at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
	at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)
	at com.sun.deploy.net.CrossDomainXML$3.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at com.sun.deploy.net.CrossDomainXML.privilegedConnect(Unknown Source)
	at com.sun.deploy.net.CrossDomainXML.check(Unknown Source)
	at com.sun.deploy.net.CrossDomainXML.check(Unknown Source)
	at com.sun.javaws.security.JavaWebStartSecurity.checkURLPermissionHelper(Unknown Source)
	at com.sun.javaws.security.JavaWebStartSecurity.checkPermission(Unknown Source)
	at sun.net.www.protocol.http.HttpURLConnection.URLtoSocketPermission(Unknown Source)
	at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
	at testapp.Testapp.fetchHtml(Testapp.java:31)
	at testapp.Testapp.<init>(Testapp.java:19)
	at testapp.Testapp.main(Testapp.java:49)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at com.sun.javaws.Launcher.executeApplication(Unknown Source)
	at com.sun.javaws.Launcher.executeMainClass(Unknown Source)
	at com.sun.javaws.Launcher.doLaunchApp(Unknown Source)
	at com.sun.javaws.Launcher.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Caused by: <eval>:34 TypeError: com.sun.deploy.net.proxy.SunAutoProxyHandler@74a3b2dc has no such function "dnsResolve"
	at jdk.nashorn.internal.runtime.ECMAErrors.error(ECMAErrors.java:56)
	at jdk.nashorn.internal.runtime.ECMAErrors.typeError(ECMAErrors.java:212)
	at jdk.nashorn.internal.runtime.ECMAErrors.typeError(ECMAErrors.java:184)
	at jdk.nashorn.internal.runtime.ECMAErrors.typeError(ECMAErrors.java:171)
	at jdk.nashorn.internal.runtime.linker.NashornBottomLinker.linkBean(NashornBottomLinker.java:118)
	at jdk.nashorn.internal.runtime.linker.NashornBottomLinker.getGuardedInvocation(NashornBottomLinker.java:73)
	at jdk.internal.dynalink.support.CompositeGuardingDynamicLinker.getGuardedInvocation(CompositeGuardingDynamicLinker.java:124)
	at jdk.internal.dynalink.support.LinkerServicesImpl.getGuardedInvocation(LinkerServicesImpl.java:144)
	at jdk.internal.dynalink.DynamicLinker.relink(DynamicLinker.java:232)
	at jdk.nashorn.internal.scripts.Script$\^eval\_.dnsResolve(<eval>:34)
	at jdk.nashorn.internal.scripts.Script$\^eval\_.FindProxyForURL(<eval>:188)
	at jdk.nashorn.internal.runtime.ScriptFunctionData.invoke(ScriptFunctionData.java:502)
	at jdk.nashorn.internal.runtime.ScriptFunction.invoke(ScriptFunction.java:206)
	at jdk.nashorn.internal.runtime.ScriptRuntime.apply(ScriptRuntime.java:378)
	at jdk.nashorn.api.scripting.ScriptObjectMirror.callMember(ScriptObjectMirror.java:179)
	at jdk.nashorn.api.scripting.NashornScriptEngine.invokeImpl(NashornScriptEngine.java:508)
	... 32 more

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
package testapp;

import java.awt.*;
import java.io.*;
import java.net.*;
import java.util.regex.*;

import javax.swing.*;

public class Testapp {
        public Testapp() {
                JFrame frame = new JFrame("Testapp");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                try {
                        frame.add(new JScrollPane(new JTextArea(Testapp.fetchHtml("http://www.google.de"))));
                }
                catch( Exception e ) {
                        e.printStackTrace();
                }
                frame.pack();
                frame.setVisible(true);
        }


        public static String fetchHtml(String url) throws IOException, URISyntaxException {
                URL url_ = new URL(url);
                try (   InputStream stream = url_.openConnection().getInputStream();
                        InputStreamReader isr = new InputStreamReader(stream);
                        BufferedReader in = new BufferedReader(isr);) {

                        StringBuilder sb = new StringBuilder();
                        String line;
                        while( (line = in.readLine()) != null ) {
                                sb.append(line).append("\n");
                        }
                        return sb.toString();
                }
        }


        public static void main(String[] args) {
                SwingUtilities.invokeLater(new Runnable() {
                        @Override
                        public void run() {
                                new Testapp();
                        }
                });
        }
}
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Not using an autoconfig-script and setting a proxy manually works but is not feasible in a corporate environment where more than one proxy must be used for different destinations.