[Android] Move Xvfb and TimeProfile from run_tests.py into individual files.

build/android/pylib/utils/xvfb.py

+# Copyright (c) 2013 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.
+
+import os
+import signal
+import subprocess
+import sys
+import time
+
+
+def _IsLinux():
+  """Return True if on Linux; else False."""
+  return sys.platform.startswith('linux')
+
+
+class Xvfb(object):
+  """Class to start and stop Xvfb if relevant.  Nop if not Linux."""
+
+  def __init__(self):
+    self._pid = 0
+
+  def Start(self):
+    """Start Xvfb and set an appropriate DISPLAY environment.  Linux only.
+
+    Copied from tools/code_coverage/coverage_posix.py
+    """
+    if not _IsLinux():
+      return
+    proc = subprocess.Popen(['Xvfb', ':9', '-screen', '0', '1024x768x24',
+                             '-ac'],
+                            stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
+    self._pid = proc.pid
+    if not self._pid:
+      raise Exception('Could not start Xvfb')
+    os.environ['DISPLAY'] = ':9'
+
+    # Now confirm, giving a chance for it to start if needed.
+    for _ in range(10):
+      proc = subprocess.Popen('xdpyinfo >/dev/null', shell=True)
+      _, retcode = os.waitpid(proc.pid, 0)
+      if retcode == 0:
+        break
+      time.sleep(0.25)
+    if retcode != 0:
+      raise Exception('Could not confirm Xvfb happiness')
+
+  def Stop(self):
+    """Stop Xvfb if needed.  Linux only."""
+    if self._pid:
+      try:
+        os.kill(self._pid, signal.SIGKILL)
+      except:
+        pass
+      del os.environ['DISPLAY']
+      self._pid = 0