Make WindowTree::SetModal() take the type.

ui/base/mojo/ui_base_types_struct_traits.h

Index: ui/base/mojo/ui_base_types_struct_traits.h
diff --git a/ui/base/mojo/ui_base_types_struct_traits.h b/ui/base/mojo/ui_base_types_struct_traits.h
new file mode 100644
index 0000000000000000000000000000000000000000..55d57df2d567e4e1f56f5beb5272f4b273c38fef
--- /dev/null
+++ b/ui/base/mojo/ui_base_types_struct_traits.h
@@ -0,0 +1,55 @@
+// 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 UI_BASE_MOJO_UI_BASE_TYPES_STRUCT_TRAITS_H_
+#define UI_BASE_MOJO_UI_BASE_TYPES_STRUCT_TRAITS_H_
+
+#include "mojo/public/cpp/bindings/enum_traits.h"
+#include "ui/base/mojo/ui_base_types.mojom.h"
+#include "ui/base/ui_base_types.h"
+
+namespace mojo {
+
+template <>
+struct EnumTraits<ui::mojom::ModalType, ui::ModalType> {
+  static ui::mojom::ModalType ToMojom(ui::ModalType modal_type) {
+    switch (modal_type) {
+      case ui::MODAL_TYPE_NONE:
+        return ui::mojom::ModalType::NONE;
+      case ui::MODAL_TYPE_WINDOW:
+        return ui::mojom::ModalType::WINDOW;
+      case ui::MODAL_TYPE_CHILD:
+        return ui::mojom::ModalType::CHILD;
+      case ui::MODAL_TYPE_SYSTEM:
+        return ui::mojom::ModalType::SYSTEM;
+      default:
+        NOTREACHED();
+        return ui::mojom::ModalType::NONE;
+    }
+  }
+
+  static bool FromMojom(ui::mojom::ModalType modal_type, ui::ModalType* out) {
+    switch (modal_type) {
+      case ui::mojom::ModalType::NONE:
+        *out = ui::MODAL_TYPE_NONE;
+        return true;
+      case ui::mojom::ModalType::WINDOW:
+        *out = ui::MODAL_TYPE_WINDOW;
+        return true;
+      case ui::mojom::ModalType::CHILD:
+        *out = ui::MODAL_TYPE_CHILD;
+        return true;
+      case ui::mojom::ModalType::SYSTEM:
+        *out = ui::MODAL_TYPE_SYSTEM;
+        return true;
+      default:
+        NOTREACHED();
+        return false;
+    }
+  }
+};
+
+}  // namespace mojo
+
+#endif  // UI_BASE_MOJO_WINDOW_OPEN_DISPOSITION_STRUCT_TRAITS_H_