Several WebGL1 extensions became features
If I recall correctly, WebGL extensions could be queried for video card support. We set a couple prefs to disable these (webgl.disable-extensions and webgl.min_capability_mode), but we should double-check that this change hasn't re-enabled anything that can be queried for video card support: https://bugzilla.mozilla.org/show_bug.cgi?id=890379
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