<AWT Dev> RFR: 8060202: [macosx] Test closed/java/awt/Choice/GetSizeTest/GetSizeTest fails only in MacOSX(10.10)

[Sergey Bylokhov]

This test is rarely failed(once per a few months), it even was not added to the problem list. And most probably it is caused by some system setup issues.

So I just apply some common cleanups:
 - A little bigger delays
 - The frame to the center of the screen
 - The frame is disposed at the end of the test

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Commit messages:
 - Update GetSizeTest.java

Changes: https://git.openjdk.java.net/jdk/pull/822/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=822&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8060202
  Stats: 30 lines in 1 file changed: 6 ins; 9 del; 15 mod
  Patch: https://git.openjdk.java.net/jdk/pull/822.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/822/head:pull/822

PR: https://git.openjdk.java.net/jdk/pull/822