IMHO the huge advantage of an env var is that it can apply to all profiles at once which makes testing easier. Wayland testing already works good this way. Something like `PR_GetEnv("MOZ_USE_EGL")` could be used for testing. Then, when it's getting enabled by default it should be inverted to `MOZ_USE_GLX`.
Bug 788319 Comment 65 Edit History
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IMHO the huge advantage of an env var is that it can apply to all profiles at once which makes testing easier. Wayland testing already works good this way. Something like `PR_GetEnv("MOZ_USE_EGL")` could be used for testing. Then, when it's getting enabled by default it should be inverted to `MOZ_USE_GLX`. (Or something like MOZ_GL=EGL, I don't know.)