If try builds are green and local testing looks good, it might be fine to merge EGL enabled by default and allow switching back to GLX by MOZ_USE_GLX env var. X11 has a GPU process, an edge case problem like surfman had wouldn't break Firefox.
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If try builds are green and local testing looks good, it might be fine to merge EGL enabled by default and allow switching back to GLX by MOZ_USE_GLX env var. X11 has a GPU process, an edge case problem like surfman had wouldn't break Nightly.