Use GL rather than EGL by default on linux....

Use GL rather than EGL by default on linux.

Debug Chromium builds display an error if they don't find EGL, even if GLX is available. This prompts people to install the EGL packages, even though that probably isn't their issue.

Also, it looks like EGL, even if available, has some issues.

If GLX isn't available, it still falls back to EGL.

--use-gl=desktop should not be required to force use of GLX on boxes that also have EGL installed.

Changed LOG(ERROR) to VLOG(1) if a shared library fails to load since this is not necessarily an error. Report an error only if no GL implementation can be initialized. Log which GL implementation was selected.

TEST=launch chrome with various combinations of --use-gl switch and check the log output is correct.
BUG=none


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=71472

[piman, 2011-01-14 00:32:46]

In general, that seems reasonable, but there may be some ARM environments where
there is a software GLX and an accelerated EGL. Choosing GLX first wouldn't be
best...
Ken, do you know the current status on chrome os ARM ?

[Kenneth Waters, 2011-01-14 00:42:41]

On the tegra2 system I have in front of me we have some GLX modules, but their
not loaded into the server so the glxQueryVersion() should fail.

I think on Qualcomm there is a chance that we install software OpenGL and
hardware OpenGL ES 2.0, because their driver is build on the mesa stack.  In
which case this would be a bad change.

It won't hurt us in the short term.  But at the same time I wouldn't make it
unless it fixes an actual bug.  Issue 63491 seems unrelated to this change.

[apatrick_chromium, 2011-01-14 00:45:44]

Is there a macro I can predicate the change on so it won't affect these systems?

[Kenneth Waters, 2011-01-14 00:49:45]

> Is there a macro I can predicate the change on so it won't affect these
systems?

There is, but please do not do this.

Go ahead and make this change, it won't hurt us in the short term, and the MESA
EGL package is not what most people want.  The error message is very misleading.

Can you fix the BUG#?  Can you change these LOG(ERROR)s to LOG(INFO)s and only
do a LOG(ERROR) if no backends are found?  Also a message about which back end
is actually being used would be nice.

[piman, 2011-01-14 00:51:44]

LGTM.
On Chrome OS, we can always force the flag that specifies which backend if it
becomes an issue, so go ahead.

[apatrick_chromium, 2011-01-14 01:27:36]

I tried to make the logs less confusing. PTAL.

[piman, 2011-01-14 01:50:16]

LGTM

[Kenneth Waters, 2011-01-14 17:34:31]

lgtm.

Thanks for fixing this up.