Use Xvfb in isolated testing only if use_x11 is set (reland)

ash/ash_unittests.isolate

 # Copyright (c) 2014 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.
 {
   'conditions': [
-    ['OS=="win" or chromeos==1', {
+    ['use_x11==0', {
       'variables': {
-        'files': [
+        'command': [
           '../testing/test_env.py',
           '<(PRODUCT_DIR)/ash_unittests<(EXECUTABLE_SUFFIX)',
-          '<(PRODUCT_DIR)/chrome_100_percent.pak',
-          '<(PRODUCT_DIR)/chrome_200_percent.pak',
-          '<(PRODUCT_DIR)/locales/en-US.pak',
-          '<(PRODUCT_DIR)/keyboard_resources.pak',
+          '--test-launcher-bot-mode',
         ],
       },
     }],
-    ['OS=="linux"', {
+    ['use_x11==1', {
       'variables': {
         'command': [
           '../testing/xvfb.py',
           '<(PRODUCT_DIR)',
           '<(PRODUCT_DIR)/ash_unittests',
           '--test-launcher-bot-mode',
         ],
         'files': [
           '../testing/xvfb.py',
+          '<(PRODUCT_DIR)/xdisplaycheck<(EXECUTABLE_SUFFIX)',
+        ],
+      },
+    }],
+    ['OS=="win" or chromeos==1', {
+      'variables': {
+        'files': [
+          '../testing/test_env.py',
+          '<(PRODUCT_DIR)/ash_unittests<(EXECUTABLE_SUFFIX)',
+          '<(PRODUCT_DIR)/chrome_100_percent.pak',
+          '<(PRODUCT_DIR)/chrome_200_percent.pak',
+          '<(PRODUCT_DIR)/locales/en-US.pak',
+          '<(PRODUCT_DIR)/keyboard_resources.pak',
+        ],
+      },
+    }],
+    ['OS=="linux"', {
+      'variables': {
+        'files': [
           '<(PRODUCT_DIR)/libffmpegsumo.so',
           '<(PRODUCT_DIR)/libosmesa.so',
         ],
       },
     }],
-    ['OS=="linux" and use_ozone==0', {
-      'variables': {
-        'files': [
-          '<(PRODUCT_DIR)/xdisplaycheck<(EXECUTABLE_SUFFIX)',
-        ],
-      },
-    }],
     ['OS=="win"', {
       'variables': {
-        'command': [
-          '../testing/test_env.py',
-          '<(PRODUCT_DIR)/ash_unittests.exe',
-          '--test-launcher-bot-mode',
-        ],
         'files': [
           '<(PRODUCT_DIR)/ffmpegsumo.dll',
           '<(PRODUCT_DIR)/osmesa.dll',
         ],
       },
     }],
     ['OS=="win" and (fastbuild==0 or fastbuild==1)', {
       'variables': {
         'files': [
           '<(PRODUCT_DIR)/ash_unittests.exe.pdb',
         ],
       },
     }],
   ],
   'includes': [
     '../base/base.isolate',
   ],
 }