RFR: 8367578: Additional WebKit 622.1 fixes from WebKitGTK 2.48.7

[Jay Bhaskar]

WebKitGTK 2.48.6 and 2.48.7 are bug-fix releases that improve stability, fix crashes, memory leaks, emoji rendering, WebP animation stuttering, and CSS animation issues, while also adding better font support and preventing unnecessary memory monitoring.

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

Commit messages:
 - Merge remote-tracking branch 'upstream/master' into webkitglib-2.48.7
 - update webkit to 2.48.7
 - Update webkit 2.48.6

Changes: https://git.openjdk.org/jfx/pull/1933/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1933&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8367578
  Stats: 227 lines in 41 files changed: 141 ins; 37 del; 49 mod
  Patch: https://git.openjdk.org/jfx/pull/1933.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1933/head:pull/1933

PR: https://git.openjdk.org/jfx/pull/1933