Only set the channel from ExtensionSystem if there hasn't been one set already.

chrome/common/extensions/features/feature.cc

 // Copyright (c) 2012 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.h"
 
 #include <map>
 
 #include "base/command_line.h"
 #include "base/lazy_instance.h"
@@ skipping 44 matching lines @@
   typedef std::map<std::string, VersionInfo::Channel> ChannelsMap;
   ChannelsMap channels = g_mappings.Get().channels;
   for (ChannelsMap::iterator i = channels.begin(); i != channels.end(); ++i) {
     if (i->second == channel)
       return i->first;
   }
   NOTREACHED();
   return "unknown";
 }
 
-VersionInfo::Channel g_current_channel = VersionInfo::CHANNEL_STABLE;
+const VersionInfo::Channel kDefaultChannel = VersionInfo::CHANNEL_STABLE;
+VersionInfo::Channel g_current_channel = kDefaultChannel;
 
 // TODO(aa): Can we replace all this manual parsing with JSON schema stuff?
 
 void ParseSet(const DictionaryValue* value,
               const std::string& property,
               std::set<std::string>* set) {
   const ListValue* list_value = NULL;
   if (!value->GetList(property, &list_value))
     return;
 
@@ skipping 251 matching lines @@
 // static
 chrome::VersionInfo::Channel Feature::GetCurrentChannel() {
   return g_current_channel;
 }
 
 // static
 void Feature::SetCurrentChannel(VersionInfo::Channel channel) {
   g_current_channel = channel;
 }
 
+// static
+chrome::VersionInfo::Channel Feature::GetDefaultChannel() {
+  return kDefaultChannel;
+}
+
 }  // namespace