Fix a browser crash on opening 'chrome://voicesearch' in guest mode.

chrome/browser/search/hotword_service_factory.h

Index: chrome/browser/search/hotword_service_factory.h
diff --git a/chrome/browser/search/hotword_service_factory.h b/chrome/browser/search/hotword_service_factory.h
index a29aaeb5dfb4de707c04fd481c3aa24acbe15f8d..dd67cfb98892906e78c06c216c87b1e23d6ce1bd 100644
--- a/chrome/browser/search/hotword_service_factory.h
+++ b/chrome/browser/search/hotword_service_factory.h
@@ -58,6 +58,8 @@ class HotwordServiceFactory : public MediaCaptureDevicesDispatcher::Observer,
       user_prefs::PrefRegistrySyncable* registry) OVERRIDE;
   virtual KeyedService* BuildServiceInstanceFor(
       content::BrowserContext* context) const OVERRIDE;
+  virtual content::BrowserContext* GetBrowserContextToUse(
+      content::BrowserContext* context) const OVERRIDE;
 
   // Must be called from the UI thread since the instance of
   // MediaCaptureDevicesDispatcher can only be accessed on the UI thread.