Convert TrackedPreferenceValidationDelegate into a mojo interface.

services/preferences/public/cpp/tracked_preference_validation_delegate_struct_traits.h

Index: services/preferences/public/cpp/tracked_preference_validation_delegate_struct_traits.h
diff --git a/services/preferences/public/cpp/tracked_preference_validation_delegate_struct_traits.h b/services/preferences/public/cpp/tracked_preference_validation_delegate_struct_traits.h
new file mode 100644
index 0000000000000000000000000000000000000000..46f07bd246faa0a002fccc12fb9ab8a566d79f1f
--- /dev/null
+++ b/services/preferences/public/cpp/tracked_preference_validation_delegate_struct_traits.h
@@ -0,0 +1,28 @@
+// Copyright 2017 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.
+
+#ifndef SERVICES_PREFERENCES_PUBLIC_CPP_TRACKED_PREFERENCE_VALIDATION_DELEGATE_STRUCT_TRAITS_H_
+#define SERVICES_PREFERENCES_PUBLIC_CPP_TRACKED_PREFERENCE_VALIDATION_DELEGATE_STRUCT_TRAITS_H_
+
+#include "components/user_prefs/tracked/pref_hash_store_transaction.h"
+#include "mojo/public/cpp/bindings/enum_traits.h"
+#include "services/preferences/public/interfaces/tracked_preference_validation_delegate.mojom-shared.h"
+
+namespace mojo {
+
+template <>
+struct EnumTraits<
+    ::prefs::mojom::TrackedPreferenceValidationDelegate_ValueState,
+    ::PrefHashStoreTransaction::ValueState> {
+  static prefs::mojom::TrackedPreferenceValidationDelegate_ValueState ToMojom(
+      PrefHashStoreTransaction::ValueState input);
+
+  static bool FromMojom(
+      prefs::mojom::TrackedPreferenceValidationDelegate_ValueState input,
+      PrefHashStoreTransaction::ValueState* output);
+};
+
+}  // namespace mojo
+
+#endif  // SERVICES_PREFERENCES_PUBLIC_CPP_TRACKED_PREFERENCE_VALIDATION_DELEGATE_STRUCT_TRAITS_H_