RFR(XXS): (7u60) Backport of 8027454: Do not traverse string table during G1 remark when treating them as strong roots during initial mark

[Thomas Schatzl]

Hi all,

  could I have some reviews for the following tiny backport from
8u20/9?

It disables string table unlink in the G1 remark pause. This is not
required as G1 initial mark treats them as strong roots always.

It is based on the recently posted backport RFR for JDK-8027476 for
7u60.

No changes, applied cleanly.

Webrev:
http://cr.openjdk.java.net/~tschatzl/8027454.7u60/webrev/

Original Webrev:
http://cr.openjdk.java.net/~tschatzl/8027454/webrev/

bugs.sun.com:
https://bugs.openjdk.java.net/browse/JDK-8027454

Testing:
jprt, FMW apps, specjbb2005, specjbb2013, dacapo, and lots
of other testing in the recent months

Thanks,
  Thomas