Use the DefaultSearchManager as the exclusive authority on DSE, ignoring Web Data.

chrome/browser/search_engines/default_search_manager.cc

 // Copyright 2014 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_engines/default_search_manager.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 81 matching lines @@
 }
 
 DefaultSearchManager::~DefaultSearchManager() {
 }
 
 // static
 void DefaultSearchManager::RegisterProfilePrefs(
     user_prefs::PrefRegistrySyncable* registry) {
   registry->RegisterDictionaryPref(
       kDefaultSearchProviderDataPrefName,
-      user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
+      user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
 }
 
 // static
 void DefaultSearchManager::AddPrefValueToMap(base::DictionaryValue* value,
                                              PrefValueMap* pref_value_map) {
   pref_value_map->SetValue(kDefaultSearchProviderDataPrefName, value);
 }
 
 TemplateURLData* DefaultSearchManager::GetDefaultSearchEngine(
     Source* source) const {
   if (default_search_controlled_by_policy_) {
     if (source)
       *source = FROM_POLICY;
     return prefs_default_search_.get();
   }
   if (extension_default_search_) {
     if (source)
       *source = FROM_EXTENSION;
     return extension_default_search_.get();
   }
   if (prefs_default_search_) {
     if (source)
       *source = FROM_USER;
     return prefs_default_search_.get();
   }
 
   if (source)
     *source = FROM_FALLBACK;
-  return fallback_default_search_.get();
+  return TemplateURLService::FallbackSearchEnginesDisabled()
+             ? NULL
+             : fallback_default_search_.get();

[Peter Kasting, 2014/05/07 23:38:29]

Nit: Please format as

  return TemplateURLService::FallbackSearchEnginesDisabled() ?
      NULL : fallback_default_search_.get();

[erikwright (departed), 2014/05/08 12:46:24]

Done.

 }
 
 DefaultSearchManager::Source
 DefaultSearchManager::GetDefaultSearchEngineSource() const {
   Source source;
   GetDefaultSearchEngine(&source);
   return source;
 }
 
 void DefaultSearchManager::SetUserSelectedDefaultSearchEngine(
@@ skipping 254 matching lines @@
   MergePrefsDataWithPrepopulated();
 }
 
 void DefaultSearchManager::NotifyObserver() {
   if (!change_observer_.is_null()) {
     Source source = FROM_FALLBACK;
     TemplateURLData* data = GetDefaultSearchEngine(&source);
     change_observer_.Run(data, source);
   }
 }