Convert miscellaneous RenderThreadImpl messages to mojom

content/common/native_types.mojom

 // Copyright 2016 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.
 
 module content.mojom;
 
 // This file is a collection of content types which rely on legacy IPC
 // ParamTraits for serialization. All of these should eventually be converted to
 // proper mojom definitions.
 
 [Native]
 struct FrameOwnerProperties;
 
 [Native]
 struct FrameReplicationState;
 
 [Native]
 struct RendererPreferences;
 
 [Native]
 struct ResizeParams;
 
+// NOTE: This type is only mapped and usable on Mac.
+[Native]
+enum ScrollbarButtonsPlacement;
+
+// NOTE: This type is only mapped and usable on Mac.
+[Native]
+enum ScrollerStyle;
+
 [Native]
 struct WebPreferences;
+
+// TODO(rockot): This should most likely be defined by network service mojom,
+// but the network service doesn't exist yet.
+[Native]
+enum NetworkConnectionType;