What's new in the WebKitGTK 2.48.3 release?
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  - Fix a crash introduced by the new threaded rendering implementation using Skia API.
  - Improve rendering performance by recording layers once and replaying every dirty
    region in different worker threads.
  - Fix a crash when setting WEBKIT_SKIA_GPU_PAINTING_THREADS=0.
  - Fix a reference cycle in webkitmediastreamsrc preventing its disposal.