RFR: 8272235: G1: update outdated code root fixup [v2]

[Albert Mingkun Yang]

> Simple change of updating outdated comments and certain renaming.
> 
> Test: hotspot_gc

Albert Mingkun Yang has updated the pull request incrementally with one additional commit since the last revision:

  review

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5073/files
  - new: https://git.openjdk.java.net/jdk/pull/5073/files/bcd8b8e3..ce687d4b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5073&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5073&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5073.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5073/head:pull/5073

PR: https://git.openjdk.java.net/jdk/pull/5073