RFR: 8258482 Lanai: reduce data for shape clip using bounding box

[Alexey Ushakov]

Limiting shape clip data to the bounding box of the clip and using the clearing render pass

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Commit messages:
 - 8258482 Lanai: reduce data for shape clip using bounding box of the shape

Changes: https://git.openjdk.java.net/lanai/pull/145/files
 Webrev: https://webrevs.openjdk.java.net/?repo=lanai&pr=145&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8258482
  Stats: 127 lines in 3 files changed: 54 ins; 47 del; 26 mod
  Patch: https://git.openjdk.java.net/lanai/pull/145.diff
  Fetch: git fetch https://git.openjdk.java.net/lanai pull/145/head:pull/145

PR: https://git.openjdk.java.net/lanai/pull/145