bug#34135: IceCat lacks WebGL support

["Ludovic Courtès" <ludo@gnu.org>]

Hello,

If you enable WebGL support in ‘about:config’, then stop it and run:

--8<---------------cut here---------------start------------->8---
$ export LIBGL_DRIVERS_PATH=$(guix build mesa)/lib/dri
$ icecat https://get.webgl.org
1547912837231   addons.webextension.tortm-browser-button@jeremybenthum  WARN    Please specify whether you want browser_style or not in your browser_action options.
1547912837231   addons.webextension.https-everywhere@eff.org    WARN    Please specify whether you want browser_style or not in your browser_action options.
1547912837232   addons.webextension.{d10d0bf8-f5b5-c8b4-a8b2-2b9879e08c5d}      WARN    Please specify whether you want browser_style or not in your browser_action options.
JavaScript warning: moz-extension://b84ee99d-7e50-4975-9d16-3806d330a3b2/lib/adblockplus.js, line 0: Successfully compiled asm.js code (total compilation time 1ms; not stored in cache (too small )
libGL error: MESA-LOADER: failed to retrieve device information
libGL error: unable to load driver: i915_dri.so
libGL error: driver pointer missing
libGL error: failed to load driver: i915
libGL error: MESA-LOADER: failed to retrieve device information
libGL error: unable to load driver: i915_dri.so
libGL error: driver pointer missing
libGL error: failed to load driver: i915
libGL error: unable to load driver: swrast_dri.so
libGL error: failed to load driver: swrast
JavaScript warning: https://get.webgl.org/, line 193: Error: WebGL warning: Failed to create WebGL context: WebGL creation failed: 
* Error during native OpenGL init.
* Exhausted GL driver caps.
* Exhausted GL driver options.
JavaScript warning: https://get.webgl.org/, line 197: Error: WebGL warning: Failed to create WebGL context: WebGL creation failed: 
* Error during native OpenGL init.
* Exhausted GL driver caps.
* Exhausted GL driver options.
--8<---------------cut here---------------end--------------->8---

and the web page reads:

   While your browser seems to support WebGL, it is disabled or
   unavailable.

Weird thing is that glxgears and glxinfo (from ‘mesa-utils’) both work
well.

Thoughts?

Ludo’.