Fix aura_unittests for Ozone X11.

testing/buildbot/chromium.chromiumos.json

Index: testing/buildbot/chromium.chromiumos.json
diff --git a/testing/buildbot/chromium.chromiumos.json b/testing/buildbot/chromium.chromiumos.json
index e28a15cf1881dfd26c0c44b8cf403a9ec0466da1..3285752817f5f40ed06f5c01e2ead0711b8f450f 100644
--- a/testing/buildbot/chromium.chromiumos.json
+++ b/testing/buildbot/chromium.chromiumos.json
@@ -52,6 +52,9 @@
         "test": "ash_unittests"
       },
       {
+        "args": [
+          "--ozone-platform=x11"
+        ],
         "swarming": {
           "can_use_on_swarming_builders": true
         },
@@ -501,6 +504,9 @@
         "test": "views_mus_unittests"
       },
       {
+        "args": [
+          "--ozone-platform=x11"
+        ],
         "swarming": {
           "can_use_on_swarming_builders": true
         },