8351276: Prevent redundant computeValue calls when a chain of mappings becomes observed
------------- Commit messages: - Add test case - Prevent redundant compute value calls Changes: https://git.openjdk.org/jfx/pull/1730/files Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1730&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8351276 Stats: 145 lines in 3 files changed: 138 ins; 1 del; 6 mod Patch: https://git.openjdk.org/jfx/pull/1730.diff Fetch: git fetch https://git.openjdk.org/jfx.git pull/1730/head:pull/1730 PR: https://git.openjdk.org/jfx/pull/1730
