Issue: Tests using `WebPageShim::paint` fails around 1/10 times. Fix: Execute `WebPageShim::paint` in the render thread using `PrismInvoker`. Ran tests over 100 times, no failures.
Used the initial unit test in the PR for [JDK-8202990](https://bugs.openjdk.java.net/browse/JDK-8202990). ------------- Commit messages: - 8252596: [TESTBUG] WebPageShim::paint is not thread-safe Changes: https://git.openjdk.java.net/jfx/pull/327/files Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=327&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8252596 Stats: 4 lines in 1 file changed: 3 ins; 0 del; 1 mod Patch: https://git.openjdk.java.net/jfx/pull/327.diff Fetch: git fetch https://git.openjdk.java.net/jfx pull/327/head:pull/327 PR: https://git.openjdk.java.net/jfx/pull/327
