Reland: Use xvfb with Ozone CrOS.

testing/buildbot/chromium.chromiumos.json

 {
   "Linux ChromiumOS Builder": {
     "additional_compile_targets": [
       "All"
     ]
   },
   "Linux ChromiumOS Ozone Tests (1)": {
     "gtest_tests": [
       {
         "swarming": {
@@ skipping 161 matching lines @@
         },
         "test": "gfx_unittests"
       },
       {
         "swarming": {
           "can_use_on_swarming_builders": true
         },
         "test": "gl_unittests"
       },
       {
+        "args": [
+          "--ozone-platform=x11"
+        ],
         "swarming": {
           "can_use_on_swarming_builders": true
         },
-        "test": "gl_unittests_ozonex"
+        "test": "gl_unittests_ozone"
       },
       {
         "swarming": {
           "can_use_on_swarming_builders": true
         },
         "test": "google_apis_unittests"
       },
       {
         "swarming": {
           "can_use_on_swarming_builders": true
@@ skipping 918 matching lines @@
       },
       {
         "swarming": {
           "can_use_on_swarming_builders": true
         },
         "test": "wm_unittests"
       }
     ]
   }
 }