Improve GCM enum switch type safety

components/gcm_driver/gcm_desktop_utils.cc

 // Copyright 2014 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 "components/gcm_driver/gcm_desktop_utils.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/sequenced_task_runner.h"
@@ skipping 35 matching lines @@
     case version_info::Channel::UNKNOWN:
       return GCMClient::CHANNEL_UNKNOWN;
     case version_info::Channel::CANARY:
       return GCMClient::CHANNEL_CANARY;
     case version_info::Channel::DEV:
       return GCMClient::CHANNEL_DEV;
     case version_info::Channel::BETA:
       return GCMClient::CHANNEL_BETA;
     case version_info::Channel::STABLE:
       return GCMClient::CHANNEL_STABLE;
-    default:
-      NOTREACHED();
-      return GCMClient::CHANNEL_UNKNOWN;
   }
+  NOTREACHED();
+  return GCMClient::CHANNEL_UNKNOWN;
 }
 
 std::string GetVersion() {
   return version_info::GetVersionNumber();
 }
 
 GCMClient::ChromeBuildInfo GetChromeBuildInfo(
     version_info::Channel channel,
     const std::string& product_category_for_subtypes) {
   GCMClient::ChromeBuildInfo chrome_build_info;
@@ skipping 32 matching lines @@
     const scoped_refptr<base::SequencedTaskRunner>& blocking_task_runner) {
   return std::unique_ptr<GCMDriver>(new GCMDriverDesktop(
       std::move(gcm_client_factory),
       GetChromeBuildInfo(channel, product_category_for_subtypes),
       GetChannelStatusRequestUrl(channel), GetUserAgent(channel), prefs,
       store_path, request_context, ui_task_runner, io_task_runner,
       blocking_task_runner));
 }
 
 }  // namespace gcm