[Extensions] Clean up renderer channel-related code

chrome/renderer/extensions/chrome_extensions_dispatcher_delegate.h

 // 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.
 
 #ifndef CHROME_RENDERER_EXTENSIONS_CHROME_EXTENSIONS_DISPATCHER_DELEGATE_H_
 #define CHROME_RENDERER_EXTENSIONS_CHROME_EXTENSIONS_DISPATCHER_DELEGATE_H_
 
 #include "base/macros.h"
 #include "extensions/renderer/dispatcher_delegate.h"
 
 class ChromeExtensionsDispatcherDelegate
     : public extensions::DispatcherDelegate {
  public:
   ChromeExtensionsDispatcherDelegate();
   ~ChromeExtensionsDispatcherDelegate() override;
 
  private:
   // extensions::DispatcherDelegate implementation.
   void InitOriginPermissions(const extensions::Extension* extension,
                              bool is_extension_active) override;
   void RegisterNativeHandlers(extensions::Dispatcher* dispatcher,
                               extensions::ModuleSystem* module_system,
                               extensions::ScriptContext* context) override;
   void PopulateSourceMap(
       extensions::ResourceBundleSourceMap* source_map) override;
   void RequireAdditionalModules(extensions::ScriptContext* context,
                                 bool is_within_platform_app) override;
   void OnActiveExtensionsUpdated(
       const std::set<std::string>& extensions_ids) override;
-  void SetChannel(int channel) override;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeExtensionsDispatcherDelegate);
 };
 
 #endif  // CHROME_RENDERER_EXTENSIONS_CHROME_EXTENSIONS_DISPATCHER_DELEGATE_H_