RFR: 8284680: sun.font.FontConfigManager.getFontConfig() leaks charset [v3]

[Zhengyu Gu]

> Please review this small patch that releases temporary charsets to avoid memory leak.
> 
> Test:
> 
> - [x] jdk_2d

Zhengyu Gu has updated the pull request incrementally with one additional commit since the last revision:

  Cleanup at early return

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/8187/files
  - new: https://git.openjdk.java.net/jdk/pull/8187/files/92ed6a78..2c74ef96

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=8187&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=8187&range=01-02

  Stats: 3 lines in 1 file changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8187.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8187/head:pull/8187

PR: https://git.openjdk.java.net/jdk/pull/8187