[Android] Allow setting recently visited search engines as default search engine

components/search_engines/template_url_service.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 "components/search_engines/template_url_service.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/auto_reset.h"
@@ skipping 377 matching lines @@
   // We don't have a TemplateURL with keyword.  We still may not allow this
   // keyword if there's evidence we may have created this keyword before and
   // the user renamed it (because, for instance, the keyword is a common word
   // that may interfere with search queries).  An easy heuristic for this is
   // whether the user has a TemplateURL that has been manually modified (e.g.,
   // renamed) connected to the same host.
   return !url.is_valid() || url.host().empty() ||
       CanAddAutogeneratedKeywordForHost(url.host());
 }
 
+bool TemplateURLService::ShowInPrepopulatedList(const TemplateURL* t_url) {
+  return (t_url->prepopulate_id() > 0 || t_url->created_by_policy()) &&
+      t_url->SupportsReplacement(search_terms_data());
+}
+
 bool TemplateURLService::ShowInDefaultList(const TemplateURL* t_url) {
-  return (t_url == default_search_provider_ || t_url->prepopulate_id() > 0 ||
-          t_url->created_by_policy()) &&
-         t_url->SupportsReplacement(search_terms_data());
+  return t_url == default_search_provider_ ||
+      ShowInPrepopulatedList(t_url);
 }
 
 void TemplateURLService::AddMatchingKeywords(
     const base::string16& prefix,
     bool supports_replacement_only,
     TURLsAndMeaningfulLengths* matches) {
   AddMatchingKeywordsHelper(
       keyword_to_turl_and_length_, prefix, supports_replacement_only, matches);
 }
 
@@ skipping 2063 matching lines @@
 
   if (most_recently_intalled_default) {
     base::AutoReset<DefaultSearchChangeOrigin> change_origin(
         &dsp_change_origin_, DSP_CHANGE_OVERRIDE_SETTINGS_EXTENSION);
     default_search_manager_.SetExtensionControlledDefaultSearchEngine(
         most_recently_intalled_default->data());
   } else {
     default_search_manager_.ClearExtensionControlledDefaultSearchEngine();
   }
 }