Log Message:
webkit-gtk: Update to 2.26.1

Changes:
WebKitGTK 2.26.1
================
 - Fix MSE media player with GStreamer 1.14.
 - Fix HTML alternate loads never finishing.
 - Fix web view initialization delay on first load.
 - Validate user agent string set via API.
 - Fix a crash when a web view is destroyed with accelerated compositing mode \ 
enabled.
 - Fix EGL initialization with newer versions of Mesa.
 - Do not enable the sandbox inside docker.
 - Fix several crashes and rendering issues.

Thanks to <wiz> for approving update during freeze!