RFR: 8271060: Merge G1CollectedHeap::determine_start_concurrent_mark_gc and G1Policy::decide_on_conc_mark_initiation [v2]

[Thomas Schatzl]

> Hi all,
> 
>   can I have reviews for this merge of two methods that have the same purpose: determine whether this pause should be a concurrent start pause. The reason for this merge is that `G1CollectedHeap::determine_start_concurrent_mark_gc` just calls the other, and
>   - is the only caller
>   - only adds another condition of the same type that `G1Policy::decide_on_conc_mark_initiation` does at the beginning
>   - adds some return value checking and return value
> which all imho fit into `G1Policy::decide_on_conc_mark_initiation` too.
> 
> It also reduces `G1CollectedHeap` a bit. The main reason for me to put this in the new location is basically that that additional condition in  `G1CollectedHeap::determine_start_concurrent_mark_gc` makes all conditions for that decision be located closer together.
> 
> If you think otherwise and this is a bad idea, I will close this PR.
> 
> Testing: manual gc/g1 runs
> 
> Thanks,
>   Thomas

Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:

  ayang review

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4867/files
  - new: https://git.openjdk.java.net/jdk/pull/4867/files/bf8d44d1..0393b5f2

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4867&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4867&range=00-01

  Stats: 13 lines in 3 files changed: 1 ins; 3 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4867.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4867/head:pull/4867

PR: https://git.openjdk.java.net/jdk/pull/4867