allow usage of transparent visuals when using xvfb

testing/xvfb.py

Index: testing/xvfb.py
diff --git a/testing/xvfb.py b/testing/xvfb.py
index 2b17d965d32ba5a106c7fcdb537742c64534e9dd..dd31c9c059d278d6951979e0329cc57b52a13d58 100755
--- a/testing/xvfb.py
+++ b/testing/xvfb.py
@@ -81,6 +81,7 @@ def start_xvfb(env, build_dir, xvfb_path='Xvfb', display=':9'):
   env['DISPLAY'] = display
   xvfb_proc = None
   openbox_proc = None
+  xcompmgr_proc = None
 
   try:
     xvfb_cmd = [xvfb_path, display, '-screen', '0', '1280x800x24', '-ac',
@@ -98,18 +99,24 @@ def start_xvfb(env, build_dir, xvfb_path='Xvfb', display=':9'):
       print 'Xvfb output:'
       for l in xvfb_proc.communicate()[0].splitlines():
         print '> %s' % l
-      return (None, None)
+      return (None, None, None)
 
     # Some ChromeOS tests need a window manager.
     openbox_proc = subprocess.Popen('openbox', stdout=subprocess.PIPE,
                                     stderr=subprocess.STDOUT, env=env)
+
+    # Some tests need a compositing manager to make use of transparent visuals.
+    xcompmgr_proc = subprocess.Popen('xcompmgr', stdout=subprocess.PIPE,
+                                     stderr=subprocess.STDOUT, env=env)
   except OSError as e:
-    print >> sys.stderr, 'Failed to start Xvfb or Openbox: %s' % str(e)
+    print >> sys.stderr, 'Failed to start Xvfb or Openbox or xcompmgr: %s' % \
+      str(e)
     kill(xvfb_proc)
     kill(openbox_proc)
-    return (None, None)
+    kill(xcompmgr_proc)
+    return (None, None, None)
 
-  return (xvfb_proc, openbox_proc)
+  return (xvfb_proc, openbox_proc, xcompmgr_proc)
 
 
 def run_executable(cmd, build_dir, env):
@@ -119,15 +126,18 @@ def run_executable(cmd, build_dir, env):
   """
   xvfb = None
   openbox = None
+  xcompmgr = None
   if should_start_xvfb(env):
-    (xvfb, openbox) = start_xvfb(env, build_dir)
-    if not xvfb or not xvfb.pid or not openbox or not openbox.pid:
+    (xvfb, openbox, xcompmgr) = start_xvfb(env, build_dir)
+    if not xvfb or not xvfb.pid or not openbox or not openbox.pid or \
+       not xcompmgr or not xcompmgr.pid:
       return 1
   try:
     return test_env.run_executable(cmd, env)
   finally:
     kill(xvfb)
     kill(openbox)
+    kill(xcompmgr)
 
 
 def main():