[8u60] RFR backport of 8065358: Refactor G1s usage of save_marks and reduce related races

[Thomas Schatzl]

Hi all,

  can I have reviews for the backport of "8065358: Refactor G1s usage of
save_marks and reduce related races" to 8u60?

It is a change that eases backporting the next change, 8060025.

It did only apply with minor changes, so I need re-reviews. The problem
has been that in jdk9 isHumongous() (and friends) have been renamed to
is_humongous() (in g1Allocator.cpp), and there is a typo fix in a
comment (behaviour -> behavior, second hunk in heapRegion.cpp).

Full 8u60 changeset:
http://cr.openjdk.java.net/~tschatzl/8065358-8u60/webrev.8u60/
Diff changest:
http://cr.openjdk.java.net/~tschatzl/8065358-8u60/webrev.8u60.fix/

CR:
https://bugs.openjdk.java.net/browse/JDK-8065358

Original change:
http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/760030342f09

Testing: jprt

Thanks,
  Thomas