[jfx25u] RFR: 8368879: Intermittent crash on exit when disposing MTLRTTextureData

[Ambarish Rapte]

This is metal specific change that fixes Intermittent crash on exit in MTLRTTextureData::dispose() during toolkit shutdown

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

Commit messages:
 - Backport 1b16ebaa8c583ce6094ad5717969967b8c9f2c9e

Changes: https://git.openjdk.org/jfx25u/pull/33/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx25u&pr=33&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8368879
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx25u/pull/33.diff
  Fetch: git fetch https://git.openjdk.org/jfx25u.git pull/33/head:pull/33

PR: https://git.openjdk.org/jfx25u/pull/33