What's new in the WebKitGTK+ 2.16.4 release?
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  - Fix web process deadlock when seeking youtube videos.
  - Fix blob downloads.
  - Improve theme rendering performance when using GTK+ >= 3.20.
  - Fix positioning of popup menus in Wayland.
  - Fix several crashes and rendering issues.
  - Security fixes: CVE-2017-2538.