[Extensions] Move Feature channel code into //extensions

chrome/common/extensions/features/feature_channel.cc

-// Copyright 2013 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 "chrome/common/extensions/features/feature_channel.h"
-
-#include "components/version_info/version_info.h"
-
-namespace {
-
-const version_info::Channel kDefaultChannel = version_info::Channel::STABLE;
-version_info::Channel g_current_channel = kDefaultChannel;
-
-}  // namespace
-
-namespace extensions {
-
-version_info::Channel GetCurrentChannel() {
-  return g_current_channel;
-}
-
-void SetCurrentChannel(version_info::Channel channel) {
-  g_current_channel = channel;
-}
-
-version_info::Channel GetDefaultChannel() {
-  return kDefaultChannel;
-}
-
-ScopedCurrentChannel::ScopedCurrentChannel(version_info::Channel channel)
-    : original_channel_(version_info::Channel::UNKNOWN) {
-  original_channel_ = GetCurrentChannel();
-  SetCurrentChannel(channel);
-}
-
-ScopedCurrentChannel::~ScopedCurrentChannel() {
-  SetCurrentChannel(original_channel_);
-}
-
-}  // namespace extensions