Integrated: 8261646: Crash in MTLBlitLoops when Metal API Validation enabled

[Alexey Ushakov]

Flush texture buffer

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Commit messages:
 - 8261646: Crash in MTLBlitLoops when Metal API Validation enabled

Changes: https://git.openjdk.java.net/lanai/pull/198/files
 Webrev: https://webrevs.openjdk.java.net/?repo=lanai&pr=198&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8261646
  Stats: 8 lines in 1 file changed: 8 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/lanai/pull/198.diff
  Fetch: git fetch https://git.openjdk.java.net/lanai pull/198/head:pull/198

PR: https://git.openjdk.java.net/lanai/pull/198