What's new in the WebKitGTK 2.51.1 release?
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  - Use the GPU process for WebGL by default.
  - Add initial API for web extensions.
  - Add API to handle WebXR permission requests.
  - Add new API to query the immersive session status.
  - Improve text rendering performance
  - Compute the layers tile size, using a different strategy depending on whether
    GPU rendering is enabled.
  - Add support for run loop observers that are now used to replace the layer flush
    timer and properly implement the opportunistic task scheduler.
  - Fix rendering fo gradients with hue interpolation method.
  - Fix rendering of layers with fractional transforms.
  - Fix pasting image data (like image/png) from the clipboard.
  - Remove support for building with libsoup2.
  - Fix several crashes and rendering issues.
  - Translation updates: Bulgarian, Slovenian, Swedish.