RFR: 8282716: [macos] Enable javax/swing/JScrollPane/TestMouseWheelScroll.java on macos

[Prasanta Sadhukhan]

The test was failing on macos and was excluded in macos because the viewposition was not changed after mouse wheel scroll. Seems like mouse wheel scroll direction is opposite in macos compared to windows etc so if we try to down-wheel scroll in macos when view position is at center of viewport (say element 3 is selected out of visible 7 elements), it cannot change viewposition as it cannot "scroll up" (since we are already at topmost viewport) whereas in windows, when we do down-wheel scroll in mouse wheel, it "scroll down" the viewport so viewposition is changed.

Fix is to use opposite scrolling motion in macos to check mouse wheel scroll is happening, which is what the testcase is meant for. CI testing of this test on all platform is ok.

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Commit messages:
 - 8282716: [macos] Enable javax/swing/JScrollPane/TestMouseWheelScroll.java on macos

Changes: https://git.openjdk.java.net/jdk/pull/8123/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8123&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8282716
  Stats: 6 lines in 1 file changed: 4 ins; 1 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8123.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8123/head:pull/8123

PR: https://git.openjdk.java.net/jdk/pull/8123