Update run_telemetry_benchmark_as_googletest to support --xvfb flag.

This CL follows how run_telemetry_as_googletest.py handles --xvfb flag.

BUG=717738

Change-Id: I0bb746d18be7818c782b7086ca96605a60af0761
Reviewed-on: https://chromium-review.googlesource.com/595227
Commit-Queue: Yuzhu Shen <yzshen@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491092}

testing/scripts/run_telemetry_benchmark_as_googletest.py

@@ -48,19 +48,11 @@ def main():
       '--isolated-script-test-chartjson-output', required=False)
   parser.add_argument('--xvfb', help='Start xvfb.', action='store_true')
   args, rest_args = parser.parse_known_args()
-  xvfb_proc = None
-  openbox_proc = None
-  xcompmgr_proc = None
   env = os.environ.copy()
   # Assume we want to set up the sandbox environment variables all the
   # time; doing so is harmless on non-Linux platforms and is needed
   # all the time on Linux.
   env[CHROME_SANDBOX_ENV] = CHROME_SANDBOX_PATH
-  if args.xvfb and xvfb.should_start_xvfb(env):
-    xvfb_proc, openbox_proc, xcompmgr_proc = xvfb.start_xvfb(env=env,
-                                                             build_dir='.')
-    assert xvfb_proc and openbox_proc and xcompmgr_proc, 'Failed to start xvfb'
-  try:
   tempfile_dir = tempfile.mkdtemp('telemetry')
   valid = True
   failures = []
@@ -70,10 +62,15 @@ def main():
 
   results = None
   try:
-      rc = common.run_command([sys.executable] + rest_args + [
+    cmd = [sys.executable] + rest_args + [
       '--output-dir', tempfile_dir,
       '--output-format=json-test-results',
-      ], env=env)
+    ]
+    if args.xvfb:
+      rc = xvfb.run_executable(cmd, env)
+    else:
+      rc = common.run_command(cmd, env=env)
+
     # If we have also output chartjson read it in and return it.
     # results-chart.json is the file name output by telemetry when the
     # chartjson output format is included
@@ -126,11 +123,6 @@ def main():
   json.dump(json_test_results, args.isolated_script_test_output)
   return rc
 
-  finally:
-    xvfb.kill(xvfb_proc)
-    xvfb.kill(openbox_proc)
-    xvfb.kill(xcompmgr_proc)
-
 
 # This is not really a "script test" so does not need to manually add
 # any additional compile targets.