Fixed dcheck failure when other search provider's favicon url is upda…

…ted.

browser/search_engines/search_engine_provider_service.cc

@@ -15,6 +15,7 @@
 #include "chrome/browser/search_engines/template_url_service_factory.h"
 #include "components/prefs/pref_service.h"
 #include "components/search_engines/prepopulated_engines.h"
+#include "components/search_engines/search_engines_pref_names.h"
 #include "components/search_engines/template_url_data_util.h"
 #include "components/search_engines/template_url_prepopulate_data.h"
 #include "components/search_engines/template_url_service.h"
@@ -110,6 +111,33 @@ void SearchEngineProviderService::UseExtensionSearchProvider() {
     otr_template_url_service_->Add(std::move(turl));
   }
 
+  // Clear default provider's guid to prevent unnecessary
+  // |kDefaultSearchProviderDataPrefName| update when search provider's favicon
+  // url is updated. If this is not cleared,  previous non-extension default
+  // search provider's guid is stored.
+  // For example, TemplateURLService::MaybeUpdateDSEViaPrefs() could update
+  // |kDefaultSearchProviderDataPrefName| if previous default search
+  // provider is qwant and current one is from extension and user searches
+  // with qwant keyword(:q) and it's favicon url is updated.
+  // Why we should prevent this? If not prevented, this user pref is updated.
+  // Then, this update pref's data is loaded again by
+  // DefaultSearchManager::LoadDefaultSearchEngineFromPrefs().
+  // Here, we have different behavior from upstream.
+  // In upstream, DSM still get extension's provider data from
+  // |pref_service_->GetDictionary(kDefaultSearchProviderDataPrefName)| because
+  // extension controlled prefs has more higher priority than user set pref.
+  // So, still DefaultSearchManager::extension_default_search_| stores extension
+  // search provider.
+  // Howeveer, we manually set |kDefaultSearchProviderDataPrefName|. So,
+  // It's replaced with qwant provider. It was extension search provider.
+  // This only happens when |kSyncedDefaultSearchProviderGUID| and favicon
+  // udpated search provider is same. (See the condition in
+  // TemplateURLService::MaybeUpdateDSEViaPrefs())
+  // And there is no side-effect when this prefs update is skipped because
+  // it can be updated again when qwant is default search provider.
+  otr_profile_->GetPrefs()->SetString(prefs::kSyncedDefaultSearchProviderGUID,
+                                      std::string());
+
   otr_profile_->GetPrefs()->Set(
       DefaultSearchManager::kDefaultSearchProviderDataPrefName,
       *TemplateURLDataToDictionary(data));