RFR: 8272609: Add string deduplication support to SerialGC [v3]

[Denghui Dong]

> Hi team,
> 
> Please help review this change to add string deduplication support to SerialGC.
> 
> Thanks,
> Denghui

Denghui Dong has updated the pull request incrementally with one additional commit since the last revision:

  fix build problem

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5153/files
  - new: https://git.openjdk.java.net/jdk/pull/5153/files/d7a7c68a..564612e0

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5153&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5153&range=01-02

  Stats: 97 lines in 7 files changed: 49 ins; 41 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5153.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5153/head:pull/5153

PR: https://git.openjdk.java.net/jdk/pull/5153