[cast_channel] Make cast_channel related files not depend on "cast_channel.h"

extensions/browser/api/cast_channel/cast_channel_type_util.cc

Index: extensions/browser/api/cast_channel/cast_channel_type_util.cc
diff --git a/extensions/browser/api/cast_channel/cast_channel_type_util.cc b/extensions/browser/api/cast_channel/cast_channel_type_util.cc
new file mode 100644
index 0000000000000000000000000000000000000000..98e98c3f55e239ec4bb5b224f19745cf4ad99686
--- /dev/null
+++ b/extensions/browser/api/cast_channel/cast_channel_type_util.cc
@@ -0,0 +1,33 @@
+// 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.
+
+#include "extensions/browser/api/cast_channel/cast_channel_type_util.h"
+
+namespace extensions {
+namespace api {
+namespace cast_channel {
+
+api::cast_channel::ReadyState ToReadyState(
+    ::cast_channel::ReadyState ready_state) {
+  return static_cast<api::cast_channel::ReadyState>(ready_state);

[imcheng, 2017/05/24 22:11:23]

static_cast from one enum to another isn't really safe. Again I think switch
statements is safer here (though a bit more verbose)

[zhaobin, 2017/05/25 00:49:23]

Done.

+}
+
+api::cast_channel::ChannelError ToChannelError(
+    ::cast_channel::ChannelError channel_error) {
+  return static_cast<api::cast_channel::ChannelError>(channel_error);
+}
+
+api::cast_channel::ChannelAuthType ToChannelAuthType(
+    ::cast_channel::ChannelAuthType channel_auth) {
+  return static_cast<api::cast_channel::ChannelAuthType>(channel_auth);
+}
+
+::cast_channel::ChannelAuthType ToChannelAuthTypeInternal(
+    api::cast_channel::ChannelAuthType channel_auth) {
+  return static_cast<::cast_channel::ChannelAuthType>(channel_auth);
+}
+
+}  // namespace cast_channel
+}  // namespace api
+}  // namespace extensions