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

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/controllers/manager.py

Index: third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/controllers/manager.py
diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/controllers/manager.py b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/controllers/manager.py
index 6a792fcadb8a06fd9119c6fe3cd0febfc96109df..fef6499b9e42e1a319d209cde9c7efa69b7cde61 100644
--- a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/controllers/manager.py
+++ b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/controllers/manager.py
@@ -332,6 +332,8 @@ class Manager(object):
                 _log.error("Build check failed")
                 return exit_code
 
+        self._port.setup_test_run()

[qyearsley, 2017/04/14 18:25:40]

I moved this line here so that it happens before the system dependency check on
linux, and so that starting xvfb can be done in Port.setup_test_run, which
seemed like the most obvious place to do it. But, this might change behavior.

The alternatives would be:
 - Add a separate _start_xvfb_if_necessary and call it here, and keep
setup_test_run down below.
 - In the linux port, make check_sys_deps responsible for starting xvfb if
necessary.

[Dirk Pranke, 2017/04/14 21:44:08]

I think moving the order of the calls is fine, but you should move everything
before check_sys_deps(), i.e., call that last in the function so that everything
else is ready as much as possible.

[qyearsley, 2017/04/18 17:58:35]

Done.

+
         # Check that the system dependencies (themes, fonts, ...) are correct.
         if not self._options.nocheck_sys_deps:
             self._printer.write_update("Checking system dependencies ...")
@@ -349,7 +351,6 @@ class Manager(object):
         # Create the output directory if it doesn't already exist.
         self._port.host.filesystem.maybe_make_directory(self._results_directory)
 
-        self._port.setup_test_run()
         return exit_codes.OK_EXIT_STATUS
 
     def _run_tests(self, tests_to_run, tests_to_skip, repeat_each, iterations,