Use Xvfb in isolated testing only if use_x11 is set

chrome/unit_tests.isolate

Index: chrome/unit_tests.isolate
diff --git a/chrome/unit_tests.isolate b/chrome/unit_tests.isolate
index 446550b8e67a42c243050cce4e5191c043cfe43b..94099442c27df14021cdbfada3bbcb57a3787803 100644
--- a/chrome/unit_tests.isolate
+++ b/chrome/unit_tests.isolate
@@ -39,7 +39,7 @@
         ],
       },
     }],
-    ['OS=="linux"', {
+    ['OS=="linux" and use_x11==1', {
       'variables': {
         'command': [
           '../testing/xvfb.py',
@@ -52,16 +52,16 @@
         ],
         'files': [
           '../testing/xvfb.py',
-          '<(PRODUCT_DIR)/libffmpegsumo.so',
-          '<(PRODUCT_DIR)/libosmesa.so',
-          '<(PRODUCT_DIR)/locales/fr.pak',
+          '<(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',
+          '<(PRODUCT_DIR)/locales/fr.pak',
         ],
       },
     }],
@@ -93,7 +93,7 @@
         ],
       },
     }],
-    ['OS=="mac" or OS=="win"', {
+    ['OS=="mac" or OS=="win" or use_ozone==1', {
       'variables': {
         'command': [
           '../testing/test_env.py',