[8u] Request for approval: 8034068 Label.toString performance improvement

[Sergey Bylokhov]

Hello,
This is a direct back port from jdk 9 to jdk 8u.

Bug: https://bugs.openjdk.java.net/browse/JDK-8034068
Webrev can be found at: http://cr.openjdk.java.net/~serb/8034068/webrev%2c01
Review: 
http://mail.openjdk.java.net/pipermail/awt-dev/2014-February/006989.html
jdk9 changeset: http://hg.openjdk.java.net/jdk9/jdk9/jdk/rev/d5b153346e93

Reviewers: Artem Ananiev, Anthony Petrov

-- 
Best regards, Sergey.