Run Ozone CrOS tests with X11 platform by default.

tools/mb/mb_config.pyl

Index: tools/mb/mb_config.pyl
diff --git a/tools/mb/mb_config.pyl b/tools/mb/mb_config.pyl
index 9b24ca7f67c57f385f247a8ba3506dd14c95f290..61b2b2f6eb6e9191a57b9476a6d50a3389e2a640 100644
--- a/tools/mb/mb_config.pyl
+++ b/tools/mb/mb_config.pyl
@@ -1032,11 +1032,11 @@
     ],
 
     'chromeos_with_codecs_ozone_release_bot': [
-      'chromeos_with_codecs', 'ozone', 'release_bot',
+      'chromeos_with_codecs', 'ozone', 'default_ozone_platform_x11', 'release_bot',
     ],
 
     'chromeos_with_codecs_ozone_release_trybot': [
-      'chromeos_with_codecs', 'ozone', 'release_trybot',
+      'chromeos_with_codecs', 'ozone', 'default_ozone_platform_x11', 'release_trybot',
     ],
 
     'chromeos_with_codecs_release_bot': [
@@ -1648,6 +1648,10 @@
       'mixins': ['debug_bot', 'minimal_symbols'],
     },
 
+    'default_ozone_platform_x11': {
+      'gn_args': 'ozone_platform="x11"',
+    },
+
     'disable_nacl': {
       'gn_args': 'enable_nacl=false',
     },