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

chrome/browser/search/hotword_service_factory.cc

 // 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.
 
 #include "chrome/browser/search/hotword_service_factory.h"
 
 #include "base/prefs/pref_service.h"
+#include "chrome/browser/profiles/incognito_helpers.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/search/hotword_service.h"
 #include "chrome/common/pref_names.h"
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
 #include "components/pref_registry/pref_registry_syncable.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/browser_thread.h"
 
 using content::BrowserContext;
 using content::BrowserThread;
@@ skipping 86 matching lines @@
                              true,
                              user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
   prefs->RegisterStringPref(prefs::kHotwordPreviousLanguage,
                             std::string(),
                             user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
   prefs->RegisterBooleanPref(prefs::kHotwordAlwaysOnSearchEnabled,
                              false,
                              user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
 }
 
+content::BrowserContext* HotwordServiceFactory::GetBrowserContextToUse(
+    content::BrowserContext* context) const {
+  return chrome::GetBrowserContextRedirectedInIncognito(context);

[rpetterson, 2014/09/08 17:35:01]

With this change, this will now return the original profile when in Incognito
which will have a valid HotwordService. Even for calls such as
HotwordServiceFactory::GetForProfile. While this is fine for the
about://voicesearch page, it's not fine for the rest of hotwording which relies
on having a NULL service for incognito since hotwording should not be available
then.

I put in a fix to redirect for incognito profiles
(https://codereview.chromium.org/450763002/). Do you know what the difference
between guest mode and incognito mode is such that it doesn't work for guest
mode?

+}
+
 KeyedService* HotwordServiceFactory::BuildServiceInstanceFor(
     BrowserContext* context) const {
   return new HotwordService(Profile::FromBrowserContext(context));
 }