Used setOpaque() method to set correct background of platform window -------------
Commit messages: - 8273355: Lanai: Flickering on tooltip appearance IntelliJ IDEA 2021.2.1 Changes: https://git.openjdk.java.net/jdk/pull/5373/files Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5373&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8273355 Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod Patch: https://git.openjdk.java.net/jdk/pull/5373.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/5373/head:pull/5373 PR: https://git.openjdk.java.net/jdk/pull/5373
