graphics_GLBench: Use existing X session if possible (for factory)

The factory test relies on an X session. If we always restart a X to run
graphics_GLBench, factory test will be killed.

This CL helps GLBench to use existing X session, especially when running under
factory test environment.

BUG=chrome-os-partner:2890
TEST=(edit factory test list to enable graphics_GLbench)
     Run grahpics_GLBench in factory test, seeing the Green box in left-top
     corner; factory test is still running.

Change-Id: I976af5c69311e63c5e18ac6ccfd7b869a6b330f5
Reviewed-on: http://gerrit.chromium.org/gerrit/751
Reviewed-by: Nick Sanders <nsanders@chromium.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Tested-by: Hung-Te Lin <hungte@chromium.org>
1 file changed