[LanguageModel] Clear the model when clearing full history

components/translate/core/browser/language_model.cc

 // Copyright 2016 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/language_model.h"
 
 #include <algorithm>
 #include <map>
 #include <set>
 
@@ skipping 114 matching lines @@
   base::DictionaryValue* dict = update.Get();
   int counter_value = 0;
   // If the key |language_code| does not exist, |counter_value| stays 0.
   dict->GetInteger(language_code, &counter_value);
   dict->SetInteger(language_code, counter_value + 1);
 
   if (GetCountersSum(*dict) > kMaxCountersSum)
     DiscountAndCleanCounters(dict);
 }
 
+void LanguageModel::ClearHistory(base::Time begin, base::Time end) {
+  // Ignore all partial removals and react only to "entire" history removal.
+  bool is_entire_history = (begin == base::Time() && end == base::Time::Max());
+  if (!is_entire_history) {
+    return;
+  }
+
+  pref_service_->ClearPref(kLanguageModelCounters);
+}
+
 }  // namespace translate