add experimental param to control the triggering threshold to default Always Translate checked

components/translate/core/browser/translate_ui_delegate.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/translate/core/browser/translate_ui_delegate.h"
 
 #include "base/i18n/string_compare.h"
 #include "base/metrics/histogram_macros.h"
 #include "components/translate/core/browser/language_state.h"
 #include "components/translate/core/browser/translate_client.h"
@@ skipping 284 matching lines @@
 
   UMA_HISTOGRAM_BOOLEAN(kNeverTranslateSite, value);
 }
 
 bool TranslateUIDelegate::ShouldAlwaysTranslate() {
   return prefs_->IsLanguagePairWhitelisted(GetOriginalLanguageCode(),
                                            GetTargetLanguageCode());
 }
 
 bool TranslateUIDelegate::ShouldAlwaysTranslateBeCheckedByDefault() {
-  // After 2 clicks on Translate for the same language.
-  // We check for == 2 instead of >= 2 because if the user translates with the
+  // After N clicks on Translate for the same language.
+  // We check for == N instead of >= N because if the user translates with the
   // "Always do this?" on, then the next time the bubble won't show up.
   // The only chance the bubble will show up is after the user manually unchecks
   // "Always do this?". In that case, since it is after user explictly unchecks,
-  // we should show as it as unchecked so we only check == 2 instead of >= 2.
+  // we should show as it as unchecked so we only check == N instead of >= N.
   return ShouldAlwaysTranslate() ||
-         prefs_->GetTranslationAcceptedCount(GetOriginalLanguageCode()) == 2;
+         prefs_->ShouldAlwaysTranslateBeCheckedByDefault(
+             GetOriginalLanguageCode());
 }
 
 void TranslateUIDelegate::SetAlwaysTranslate(bool value) {
   const std::string& original_lang = GetOriginalLanguageCode();
   const std::string& target_lang = GetTargetLanguageCode();
   if (value)
     prefs_->WhitelistLanguagePair(original_lang, target_lang);
   else
     prefs_->RemoveLanguagePairFromWhitelist(original_lang, target_lang);
 
   UMA_HISTOGRAM_BOOLEAN(kAlwaysTranslateLang, value);
 }
 
 std::string TranslateUIDelegate::GetPageHost() {
   if (!translate_driver_->HasCurrentPage())
     return std::string();
   return translate_driver_->GetLastCommittedURL().HostNoBrackets();
 }
 
 }  // namespace translate