[jfx11u] RFR: 8274107: Cherry pick GTK WebKit 2.32.4 changes

[Kevin Rushforth]

Clean backport to `jfx11u` of WebKit GTK 2.32.4 fixes.

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

Commit messages:
 - 8274107: Cherry pick GTK WebKit 2.32.4 changes

Changes: https://git.openjdk.java.net/jfx11u/pull/54/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx11u&pr=54&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274107
  Stats: 1811 lines in 131 files changed: 1043 ins; 205 del; 563 mod
  Patch: https://git.openjdk.java.net/jfx11u/pull/54.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx11u pull/54/head:pull/54

PR: https://git.openjdk.java.net/jfx11u/pull/54