xvfb: set dpi to 96 (xvfb defaults to 100).

scripts/slave/xvfb.py

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Functions to setup xvfb, which is used by the linux machines.
 """
 
 import os
 import platform
 import signal
@@ skipping 54 matching lines @@
   if server_dir and os.path.exists(server_dir):
     cmd = os.path.join(server_dir, 'Xvfb.' + platform.architecture()[0])
     if not os.path.exists(cmd):
       cmd = os.path.join(server_dir, 'Xvfb')
     if not os.path.exists(cmd):
       print 'No Xvfb found in designated server path:', server_dir
       raise Exception('No virtual server')
 
   # Start a virtual X server that we run the tests in.  This makes it so we can
   # run the tests even if we didn't start the tests from an X session.
-  proc = subprocess.Popen([cmd, display, '-screen', '0', '1024x768x24', '-ac'],
+  proc = subprocess.Popen([cmd, display, '-screen', '0', '1024x768x24', '-ac',
+                           '-dpi', '96'],

[pfeifer, 2015/04/24 14:59:52]

With HiDPI becoming more popular, it's conceivable that one would want to write
tests for different DPI settings.

Is it worth making dpi an extra parameter to StartVirtualX which defaults to 96
?

                           stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
   xvfb_pid_filename = _XvfbPidFilename(slave_build_name)
   open(xvfb_pid_filename, 'w').write(str(proc.pid))
 
   # Verify that Xvfb has started by using xdisplaycheck.
   if xdisplaycheck_path and os.path.exists(xdisplaycheck_path):
     print 'Verifying Xvfb has started...'
     checkstarttime = time.time()
     xdisplayproc = subprocess.Popen([xdisplaycheck_path],
                                     stdout=subprocess.PIPE,
@@ skipping 42 matching lines @@
   if os.path.exists(xvfb_pid_filename):
     xvfb_pid = int(open(xvfb_pid_filename).read())
     print 'Stopping Xvfb with pid %d ...' % xvfb_pid
     # If the process doesn't exist, we raise an exception that we can ignore.
     try:
       os.kill(xvfb_pid, signal.SIGKILL)
     except OSError:
       print '... killing failed, presuming unnecessary.'
     os.remove(xvfb_pid_filename)
     print 'Xvfb pid file removed'