Separate xvfb.py logic into its own script

base/base.gyp

Index: base/base.gyp
diff --git a/base/base.gyp b/base/base.gyp
index 2d242bd30772006eaf6fa3621e36df126cd241ac..945d18f713f991bccd282d416abf914a6fb5b68e 100644
--- a/base/base.gyp
+++ b/base/base.gyp
@@ -452,6 +452,9 @@
           'action_name': 'isolate',
           'inputs': [
             '<(PRODUCT_DIR)/base_unittests<(EXECUTABLE_SUFFIX)',
+            '<(PRODUCT_DIR)/xdisplaycheck',
+            '<(DEPTH)/testing/test_env.py',
+            '<(DEPTH)/testing/xvfb.py',
           ],
           'conditions': [
             ['OS != "mac" and OS != "win"', {
@@ -482,6 +485,11 @@
             # TODO(maruel): Revisit the support for this at all and list each
             # individual test files instead.
             'data/file_util_unittest/',
+            '--',
+            # Wraps base_unittests under xvfb.
+            '<(DEPTH)/testing/xvfb.py',
+            '<(PRODUCT_DIR)',
+            '<(PRODUCT_DIR)/base_unittests<(EXECUTABLE_SUFFIX)',
           ],
         },
       ],