Mojo C++ bindigns: fix generated namespace when variant is specified.

mojo/public/interfaces/bindings/tests/test_variant.mojom

Index: mojo/public/interfaces/bindings/tests/test_variant.mojom
diff --git a/gpu/command_buffer/common/capabilities.mojom b/mojo/public/interfaces/bindings/tests/test_variant.mojom
similarity index 74%
copy from gpu/command_buffer/common/capabilities.mojom
copy to mojo/public/interfaces/bindings/tests/test_variant.mojom
index fd35409e940e193377d9411c182e99746220f2a7..318b6a77a93bf7a8f8e4e3a37a64ecd3859d7802 100644
--- a/gpu/command_buffer/common/capabilities.mojom
+++ b/mojo/public/interfaces/bindings/tests/test_variant.mojom
@@ -2,7 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-module gpu.mojom;
+module mojo.test;
 
-[Native]
-struct Capabilities;
+enum TestEnum {
+  VALUE1,
+  VALUE2
+};