Use Xvfb in isolated testing only if use_x11 is set

content/content_browsertests.isolate

Index: content/content_browsertests.isolate
diff --git a/content/content_browsertests.isolate b/content/content_browsertests.isolate
index 53a53fc317a968f8d65d4cd2c1a1cfb2527b810e..ef3822eaf2191e6f44512d4c26a37c027b6944fa 100644
--- a/content/content_browsertests.isolate
+++ b/content/content_browsertests.isolate
@@ -33,7 +33,7 @@
         ],
       },
     }],
-    ['OS=="linux"', {
+    ['OS=="linux" and use_x11==1', {
       'variables': {
         'command': [
           '../testing/xvfb.py',
@@ -45,17 +45,17 @@
         ],
         'files': [
           '../testing/xvfb.py',
-          '<(PRODUCT_DIR)/content_shell.pak',
-          '<(PRODUCT_DIR)/libffmpegsumo.so',
-          '<(PRODUCT_DIR)/libosmesa.so',
-          '<(PRODUCT_DIR)/libppapi_tests.so',
+          '<(PRODUCT_DIR)/xdisplaycheck<(EXECUTABLE_SUFFIX)',
         ],
       },
     }],
-    ['OS=="linux" and use_ozone==0', {
+    ['OS=="linux"', {
       'variables': {
         'files': [
-          '<(PRODUCT_DIR)/xdisplaycheck<(EXECUTABLE_SUFFIX)',
+          '<(PRODUCT_DIR)/content_shell.pak',
+          '<(PRODUCT_DIR)/libffmpegsumo.so',
+          '<(PRODUCT_DIR)/libosmesa.so',
+          '<(PRODUCT_DIR)/libppapi_tests.so',
         ],
       },
     }],
@@ -84,7 +84,7 @@
         ],
       },
     }],
-    ['OS=="mac" or OS=="win"', {
+    ['OS=="mac" or OS=="win" or use_ozone==1', {
       'variables': {
         'command': [
           '../testing/test_env.py',