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

chrome/common/extensions/features/feature.h

Index: chrome/common/extensions/features/feature.h
diff --git a/chrome/common/extensions/features/feature.h b/chrome/common/extensions/features/feature.h
index 8d5b2c4fd3f32264c8d021b9d6b6aee6d8097dd9..f0324ab7dcde19fc827a14dd74593956938f435a 100644
--- a/chrome/common/extensions/features/feature.h
+++ b/chrome/common/extensions/features/feature.h
@@ -69,7 +69,6 @@ class Feature {
   virtual ~Feature();
 
   // Gets the current channel as seen by the Feature system.
-  // Defaults to CHANNEL_STABLE.
   static chrome::VersionInfo::Channel GetCurrentChannel();
 
   // Sets the current channel as seen by the Feature system. In the browser
@@ -77,6 +76,9 @@ class Feature {
   // renderer this will need to come from an IPC.
   static void SetCurrentChannel(chrome::VersionInfo::Channel channel);
 
+  // Gets the default channel as seen by the Feature system.
+  static chrome::VersionInfo::Channel GetDefaultChannel();
+
   // Scoped channel setter. Use for tests.
   class ScopedCurrentChannel {
    public: