Use Xvfb in isolated testing only if use_x11 is set

ui/base/ui_base_unittests.isolate

Index: ui/base/ui_base_unittests.isolate
diff --git a/ui/base/ui_base_unittests.isolate b/ui/base/ui_base_unittests.isolate
index 16f6dd5fae04848172cbd51af4633d673df4fd15..f23d5761e6c1e6d4a299de01b4279b51107568b0 100644
--- a/ui/base/ui_base_unittests.isolate
+++ b/ui/base/ui_base_unittests.isolate
@@ -21,7 +21,7 @@
         ],
       },
     }],
-    ['OS=="linux"', {
+    ['OS=="linux" and use_x11==1', {
       'variables': {
         'command': [
           '../../testing/xvfb.py',
@@ -34,14 +34,14 @@
         ],
         'files': [
           '../../testing/xvfb.py',
-          '<(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)/libosmesa.so',
         ],
       },
     }],
@@ -60,7 +60,7 @@
         ],
       },
     }],
-    ['OS=="mac" or OS=="win"', {
+    ['OS=="mac" or OS=="win" or use_ozone==1', {
       'variables': {
         'command': [
           '../../testing/test_env.py',