RFR: 8291266: RenderPerfTest: missing content while rendering some primitives

[Alexey Ushakov]

Do not cause redundant endEncoder calls with batch processing of drawing primitives

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Commit messages:
 - 8291266: RenderPerfTest: missing content while rendering some primitives

Changes: https://git.openjdk.org/jdk/pull/9756/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9756&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8291266
  Stats: 6 lines in 1 file changed: 4 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/9756.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9756/head:pull/9756

PR: https://git.openjdk.org/jdk/pull/9756