[[Platform/GFX/WebGL|WebGL]] is a quite thin layer on top of GL or GLES, with an extensive conformance suite and solid lines of communication between implementers.
We currently have hardware acceleration support everywhere, though there but that is also latent support for using OSMesa subject to [https://wiki.mozilla.org/Blocklisting/Blocked_Graphics_Drivers driver blacklisting] and as a software rendererresult, [http://people.mozilla.org/~bjacob/gfx_features_stats/ does not] serve all of our users.
There is also [https://bugzilla.mozilla.org/show_bug.cgi?id=731836 a bug to add support for the Mesa llvmpipe software renderer].
Chrome is integrating the proprietary SwiftShader software renderer.