Use Xvfb in isolated testing only if use_x11 is set

ash/ash_unittests.isolate

Index: ash/ash_unittests.isolate
diff --git a/ash/ash_unittests.isolate b/ash/ash_unittests.isolate
index 918a8e0252930e5616552d84d938803334d1dfc8..b30a5d58110bffb05a2c50b5f5a82cd0bbe460b4 100644
--- a/ash/ash_unittests.isolate
+++ b/ash/ash_unittests.isolate
@@ -15,7 +15,16 @@
         ],
       },
     }],
-    ['OS=="linux"', {
+    ['use_x11==0', {
+      'variables': {
+        'command': [
+          '../testing/test_env.py',
+          '<(PRODUCT_DIR)/ash_unittests<(EXECUTABLE_SUFFIX)',
+          '--test-launcher-bot-mode',
+        ],
+      },
+    }],
+    ['use_x11==1', {
       'variables': {
         'command': [
           '../testing/xvfb.py',
@@ -25,25 +34,20 @@
         ],
         'files': [
           '../testing/xvfb.py',
-          '<(PRODUCT_DIR)/libffmpegsumo.so',
-          '<(PRODUCT_DIR)/libosmesa.so',
+          '<(PRODUCT_DIR)/xdisplaycheck<(EXECUTABLE_SUFFIX)',
         ],
       },
     }],
-    ['OS=="linux" and use_ozone==0', {
+    ['OS=="linux"', {
       'variables': {
         'files': [
-          '<(PRODUCT_DIR)/xdisplaycheck<(EXECUTABLE_SUFFIX)',
+          '<(PRODUCT_DIR)/libffmpegsumo.so',
+          '<(PRODUCT_DIR)/libosmesa.so',
         ],
       },
     }],
     ['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',