Use xvfb for the ozone linux tests

tools/mb/mb.py

Index: tools/mb/mb.py
diff --git a/tools/mb/mb.py b/tools/mb/mb.py
index 917f3c62be301aad351cf8234a38bbb2d46ee84a..cf17f20432597d49b5e44c42839fc0cb507681c6 100755
--- a/tools/mb/mb.py
+++ b/tools/mb/mb.py
@@ -1066,8 +1066,7 @@ class MetaBuildWrapper(object):
     # expected to run using xvfb. For example, Linux Desktop, X11 CrOS and
     # Ozone CrOS builds.
     use_xvfb = (self.platform == 'linux2' and
-               not android and
-               ((not ozone) or (ozone and chromeos)))
+               not android and ozone or (ozone and chromeos))

[fwang, 2017/03/20 15:10:35]

I think ((not ozone) or (ozone and chromeos)) can just be removed

[kylechar, 2017/03/20 17:03:31]

Yep, like this:

use_xvfb = (self.platform == 'linux2' and
           not android)

[Dirk Pranke, 2017/03/20 17:22:50]

So there's no non-X11 configuration we're testing any more? Or will the
configurations that don't use X11 just ignore the fact that they're running
under xvfb?

[kylechar, 2017/03/20 17:30:42]

This particular change only affects 'Ozone Linux' FYI bot, which runs two tests
with Ozone X11 now (and previously ran 0 tests total).

In general, the Ozone CrOS trybot runs a couple of tests with Ozone headless
still. If type=window_test_launcher then it will run using Xvfb. The tests
wouldn't check $DISPLAY env var and wouldn't know Xvfb was running though..

[Dirk Pranke, 2017/03/20 17:36:57]

I guess we were already assuming CrOS+Ozone==X11. Using X11 for things we know
are using Ozone still feels weird to me :).

Can we update the comments on lines 1065-1067 to make this clearer somehow?

[fwang, 2017/03/21 06:54:29]

What about this:

"... For example, Linux Desktop, X11 CrOS and Ozone builds. Note that one Ozone
build can be used to run different backends. Currently, tests are executed for
the headless and X11 backends and both can run under Xvfb.
FIXME(tonikitoo,msisov,fwang): Find a way to run tests for the Wayland backend."

[msisov, 2017/03/21 07:18:16]

Done.

 
     asan = 'is_asan=true' in vals['gn_args']
     msan = 'is_msan=true' in vals['gn_args']