RFR: 8261404: Class.getReflectionFactory() is not thread-safe [v2]

[liach]

> Simply changes this to only read the static field once to prevent `null` on second read.

liach has updated the pull request incrementally with two additional commits since the last revision:

 - sorry, reintroduced the bug in last patch
 - choose a concise name for the local var

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6870/files
  - new: https://git.openjdk.java.net/jdk/pull/6870/files/2f7c84a1..acc043ee

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6870&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6870&range=00-01

  Stats: 8 lines in 1 file changed: 2 ins; 2 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6870.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6870/head:pull/6870

PR: https://git.openjdk.java.net/jdk/pull/6870