RFR: 8282200: ShouldNotReachHere() reached by AsyncGetCallTrace after JDK-8280422 [v2]

[Johannes Bechberger]

> Fixes the mentioned bug by replacing the check in AsyncGetCallTrace using the newly introduced method `JavaThread::thread_from_jni_environment`.

Johannes Bechberger has updated the pull request incrementally with one additional commit since the last revision:

  Add changes by David Holmes

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7559/files
  - new: https://git.openjdk.java.net/jdk/pull/7559/files/8364d4b0..9f701eb0

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7559&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7559&range=00-01

  Stats: 10 lines in 2 files changed: 6 ins; 1 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7559.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7559/head:pull/7559

PR: https://git.openjdk.java.net/jdk/pull/7559