RFR 8071667 : HashMap.computeIfAbsent() adds entry that HashMap.get() does not find.

Hi, Please review my changes for 8071667 : "HashMap.computeIfAbsent() adds entry that HashMap.get() does not find" Bug: https://bugs.openjdk.java.net/browse/JDK-8071667 Webrev+specdiff: http://cr.openjdk.java.net/~bchristi/8071667/webrev.2/ The fix is to detect structural changes made by the mapping functions passed to compute() and friends, and to throw a ConcurrentModificationException. This prevents possibly adding entries in the wrong hash bin. I have updated the docs based on the prior discussion [1], making use of the new @implSpec/etc tags, as seemed sensible to me. Suggestions welcome. Automated test run is clean. If the new docs look good, I'll start a CCC. Thanks, -Brent 1. http://mail.openjdk.java.net/pipermail/core-libs-dev/2015-February/031245.ht...