RFR: 8275131: Exceptions after a touchpad gesture on macOS

[Dmitry Batrak]

This is a small fix for a mistake in JDK-8257853 implementation, replacing DECLARE_METHOD JNI lookup macro with DECLARE_STATIC_METHOD in [AWTWindow_Normal postGesture:as:a🅱].
I did not created a test for the fix, as AWT Robot doesn't currently support touchpad gestures.

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Commit messages:
 - 8275131: Exceptions after a touchpad gesture on macOS

Changes: https://git.openjdk.java.net/jdk/pull/5910/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5910&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8275131
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5910.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5910/head:pull/5910

PR: https://git.openjdk.java.net/jdk/pull/5910