RFR: 8253840: Lanai - MTLClip.beginShapeClip method uses a larger temporary buffer than needed

[Ajit Ghaisas]

Issue : A temporary buffer which is 4 times larger is allocated and filled with 0's - but only 1/4th of it is used
while copying. Fix : Corrected the size of temporary buffer. Done spacing correction at two places and also removed an
unused variable.

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Commit messages:
 - correct_temp_buff_size

Changes: https://git.openjdk.java.net/lanai/pull/110/files
 Webrev: https://webrevs.openjdk.java.net/?repo=lanai&pr=110&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253840
  Stats: 5 lines in 1 file changed: 0 ins; 1 del; 4 mod
  Patch: https://git.openjdk.java.net/lanai/pull/110.diff
  Fetch: git fetch https://git.openjdk.java.net/lanai pull/110/head:pull/110

PR: https://git.openjdk.java.net/lanai/pull/110