RFR (XXXS): 8160874: Remove typo in G1InitalMarkClosures

[Thomas Schatzl]

Hi all,

  can I have reviews for this change that fixes a typo in a class name
(G1InitalMarkClosure ->  G1InitialMarkClosure).

CR:
https://bugs.openjdk.java.net/browse/JDK-8160874
Webrev:
http://cr.openjdk.java.net/~tschatzl/8160874/webrev/
Testing:
jprt

I would like to invoke the "trivial change" clause for this to avoid
too much fuss about this.

Thanks,
  Thomas