RFR: 8191133: Ant task to fetch underscore.js requires gzip decoding option

[Hannes Wallnöfer]

Please review:

Bug: https://bugs.openjdk.java.net/browse/JDK-8191133
Webrev: http://cr.openjdk.java.net/~hannesw/8191133/webrev/

Thanks,
Hannes