RFR: 8285399: JNI exception pending in awt_GraphicsEnv.c:1432

[Phil Race]

This is a theoretical/potential case of calling JNI methods with a possible execption pending.
As noted in the eval of the bug report, we no longer follow the practice that AWT_LOCK is
called only at the start of a native method and AWT_UNLOCK at the end, if indeed we ever did.
But it seems to be implied in how they are handling exceptions.

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Commit messages:
 - 8285399

Changes: https://git.openjdk.java.net/jdk/pull/8493/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8493&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8285399
  Stats: 6 lines in 2 files changed: 6 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8493.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8493/head:pull/8493

PR: https://git.openjdk.java.net/jdk/pull/8493