C++ bindings: separate out serialization source set, have "mojom" targets optionally use serializat…

examples/serialization/serialization.mojom

Index: examples/serialization/serialization.mojom
diff --git a/mojo/public/interfaces/bindings/tests/test_included_unions.mojom b/examples/serialization/serialization.mojom
similarity index 54%
copy from mojo/public/interfaces/bindings/tests/test_included_unions.mojom
copy to examples/serialization/serialization.mojom
index 5c08681eda089a440f67369fadd07b6a4a0bd00f..5107760fdcc4aeb1529e5e40254f65566c7a8d25 100644
--- a/mojo/public/interfaces/bindings/tests/test_included_unions.mojom
+++ b/examples/serialization/serialization.mojom
@@ -1,9 +1,11 @@
 // Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
+// Use of this source code is governed by a BSD-style license that can be found
+// in the LICENSE file.
 
-module mojo.test;
+module examples;
 
-union IncludedUnion {
-  int8 a;
+struct MyStruct {
+  int32 a;
+  float b;
+  string c;
 };