RFR: 8242338: Shape clip with AA not working in J2DDemo

[Alexey Ushakov]

Implemented shape clip for MSAA rendering inside a shader

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Commit messages:
 - 8242338: Shape clip with AA not working in J2DDemo

Changes: https://git.openjdk.java.net/lanai/pull/44/files
 Webrev: https://webrevs.openjdk.java.net/lanai/44/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8242338
  Stats: 115 lines in 7 files changed: 61 ins; 2 del; 52 mod
  Patch: https://git.openjdk.java.net/lanai/pull/44.diff
  Fetch: git fetch https://git.openjdk.java.net/lanai pull/44/head:pull/44

PR: https://git.openjdk.java.net/lanai/pull/44