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

chrome/browser/search/hotword_service.h

Index: chrome/browser/search/hotword_service.h
diff --git a/chrome/browser/search/hotword_service.h b/chrome/browser/search/hotword_service.h
index f17bee910fdc679ed1a7823f5718466c35492dd0..664a56a906f9374930935533b543fd7500c2a0c1 100644
--- a/chrome/browser/search/hotword_service.h
+++ b/chrome/browser/search/hotword_service.h
@@ -6,8 +6,10 @@
 #define CHROME_BROWSER_SEARCH_HOTWORD_SERVICE_H_
 
 #include "base/basictypes.h"
+#include "base/prefs/pref_change_registrar.h"
 #include "components/keyed_service/core/keyed_service.h"
 
+class ExtensionService;
 class Profile;
 
 namespace hotword_internal {
@@ -50,9 +52,19 @@ class HotwordService : public KeyedService {
   // already loaded successfully by some other means.
   virtual bool RetryHotwordExtension();
 
+  // Control the state of the hotword extension.
+  void EnableHotwordExtension(ExtensionService* extension_service);
+  void DisableHotwordExtension(ExtensionService* extension_service);
+
+  // 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);
 };