In run-webkit-tests, start xvfb if necessary.

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/linux.py

Index: third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/linux.py
diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/linux.py b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/linux.py
index 28c22b47facd8e800034a402d621384a9ea3ad75..da1121b75800853d9c201513f69397a5be9d5a5d 100644
--- a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/linux.py
+++ b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/linux.py
@@ -65,6 +65,7 @@ class LinuxPort(base.Port):
         if not self.get_option('disable_breakpad'):
             self._dump_reader = DumpReaderLinux(host, self._build_path())
         self._original_home = None
+        self._xvfb_process = None
 
     def additional_driver_flag(self):
         flags = super(LinuxPort, self).additional_driver_flag()
@@ -104,10 +105,12 @@ class LinuxPort(base.Port):
 
     def setup_test_run(self):
         super(LinuxPort, self).setup_test_run()
+        self._start_xvfb()
         self._setup_dummy_home_dir()
 
     def clean_up_test_run(self):
         super(LinuxPort, self).clean_up_test_run()
+        self._stop_xvfb()
         self._clean_up_dummy_home_dir()
 
     #
@@ -142,6 +145,45 @@ class LinuxPort(base.Port):
         self._filesystem.rmtree(dummy_home)
         self.host.environ['HOME'] = self._original_home
 
+    def _start_xvfb(self):
+        display = self._find_display()
+        if not display:
+            _log.warn('Failed to find a free display to start Xvfb.')
+            return
+
+        _log.info('Starting Xvfb with display "%s".', display)
+        self._xvfb_process = self.host.executive.popen(
+            ['Xvfb', display, '-screen', '0', '1280x800x24', '-ac', '-dpi', '96'],
+            stderr=self.host.executive.DEVNULL)
+
+        # By setting DISPLAY here, the individual worker processes will
+        # get the right DISPLAY. Note, if this environment could be passed
+        # when creating workers, then we wouldn't need to modify DISPLAY here.
+        self.host.environ['DISPLAY'] = display
+
+        # The poll() method will return None if the process has not terminated:
+        # https://docs.python.org/2/library/subprocess.html#subprocess.Popen.poll
+        if self._xvfb_process.poll() is not None:
+            _log.warn('Failed to start Xvfb on display "%s."', display)
+
+    def _find_display(self):
+        """Tries to find a free X display, looping if necessary."""
+        # The "xvfb-run" command uses :99 by default.
+        for display_number in range(99, 120):
+            display = ':%d' % display_number
+            exit_code = self.host.executive.run_command(
+                ['xdpyinfo', '-display', display], return_exit_code=True)
+            if exit_code == 1:
+                return display
+        return None
+
+    def _stop_xvfb(self):
+        if not self._xvfb_process:
+            return
+        _log.debug('Killing Xvfb process pid %d.', self._xvfb_process.pid)
+        self._xvfb_process.kill()
+        self._xvfb_process.wait()
+
     def _path_to_driver(self, target=None):
         binary_name = self.driver_name()
         return self._build_path_with_target(target, binary_name)