[Hotword] Making enabling/disabling the setting enable/disable the hotword extension.

chrome/browser/search/hotword_service.h

 // Copyright 2013 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_SEARCH_HOTWORD_SERVICE_H_
 #define CHROME_BROWSER_SEARCH_HOTWORD_SERVICE_H_
 
 #include "base/basictypes.h"
+#include "base/prefs/pref_change_registrar.h"
 #include "components/browser_context_keyed_service/browser_context_keyed_service.h"
 
 class Profile;
 
 namespace hotword_internal {
 // Constants for the hotword field trial.
 extern const char kHotwordFieldTrialName[];
 extern const char kHotwordFieldTrialDisabledGroupName[];
 }  // namespace hotword_internal
 
@@ skipping 24 matching lines @@
   // Determine if hotwording is allowed in this profile based on field trials
   // and language.
   virtual bool IsHotwordAllowed();
 
   // Used in the case of an error with the current hotword extension. Tries
   // to reload the extension or in the case of failure, tries to re-download it.
   // Returns true upon successful attempt at reload or if the extension has
   // already loaded successfully by some other means.
   virtual bool RetryHotwordExtension();
 
+  // Control the state of the hotword extension.
+  void DisableHotwordExtension();
+  void EnableHotwordExtension();
+
+  // Handles enabling/disabling the hotword extension when the user
+  // turns it off via the settings menu.
+  void OnHotwordSearchEnabledChanged(const std::string& pref_name);
+
  private:
   Profile* profile_;
 
+  PrefChangeRegistrar pref_registrar_;
+
   DISALLOW_COPY_AND_ASSIGN(HotwordService);
 };
 
 #endif  // CHROME_BROWSER_SEARCH_HOTWORD_SERVICE_H_