Fix "unused variable" warnings.

chrome/browser/extensions/component_migration_helper.h

 // Copyright 2016 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_BROWSER_EXTENSIONS_COMPONENT_MIGRATION_HELPER_H_
 #define CHROME_BROWSER_EXTENSIONS_COMPONENT_MIGRATION_HELPER_H_
 
 #include <set>
 #include <string>
 #include <utility>
@@ skipping 106 matching lines @@
   std::set<std::string> enabled_actions_;
 
  private:
   bool IsExtensionInstalledAndEnabled(const ExtensionId& extension_id) const;
   void UnloadExtension(const ExtensionId& extension_id);
   void RemoveComponentActionPref(const std::string& component_action_id);
   std::vector<std::string> GetExtensionIdsForActionId(
       const std::string& component_action_id) const;
   std::string GetActionIdForExtensionId(const ExtensionId& extension_id) const;
 
-  Profile* const profile_;
   ComponentActionDelegate* const delegate_;
   // The ExtensionRegistry, PrefService, and ExtensionSystem, cached for
   // convenience.
   ExtensionRegistry* const extension_registry_;
   PrefService* const pref_service_;
   ExtensionSystem* const extension_system_;
 
   ScopedObserver<ExtensionRegistry, ExtensionRegistryObserver>
       extension_registry_observer_;
 
   // A list of pairs of component action ids and extension ids.
   std::vector<std::pair<std::string, ExtensionId>> migrated_actions_;
 
   DISALLOW_COPY_AND_ASSIGN(ComponentMigrationHelper);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_COMPONENT_MIGRATION_HELPER_H_