[jfx11u] Integrated: 8282099: Cherry-pick WebKit 613.1 stabilization fixes (2)

[Kevin Rushforth]

Clean backport to `jfx11u`. I tested this along with the other VS 2019 and WebKit 613.1 fixes together in the `test-kcr-11.0.15` branch.

-------------

Commit messages:
 - 8282099: Cherry-pick WebKit 613.1 stabilization fixes (2)

Changes: https://git.openjdk.java.net/jfx11u/pull/80/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx11u&pr=80&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8282099
  Stats: 186 lines in 11 files changed: 116 ins; 33 del; 37 mod
  Patch: https://git.openjdk.java.net/jfx11u/pull/80.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx11u pull/80/head:pull/80

PR: https://git.openjdk.java.net/jfx11u/pull/80