RFR: 8274466 G1: simplify G1 collector states [v2]

[Hamlin Li]

> This is a minor improvement which remove the redundant G1 Collector states usages.

Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:

  Revert wrong code

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5745/files
  - new: https://git.openjdk.java.net/jdk/pull/5745/files/e2a4eae7..9bbe1ccc

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5745&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5745&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5745.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5745/head:pull/5745

PR: https://git.openjdk.java.net/jdk/pull/5745