[LanguageModel] Clear the model when clearing full history

components/translate/core/browser/language_model_unittest.cc

Index: components/translate/core/browser/language_model_unittest.cc
diff --git a/components/translate/core/browser/language_model_unittest.cc b/components/translate/core/browser/language_model_unittest.cc
index df8b6bad29de2f8b510d0115d36a8e08fec27348..f59a31bd404f1c2a2723e010f5ae1bf468c09149 100644
--- a/components/translate/core/browser/language_model_unittest.cc
+++ b/components/translate/core/browser/language_model_unittest.cc
@@ -11,6 +11,7 @@
 using testing::ElementsAre;
 using testing::FloatEq;
 using testing::Gt;
+using testing::SizeIs;
 
 namespace {
 
@@ -105,4 +106,42 @@ TEST(LanguageModelTest, RareLanguageDiscarded) {
               ElementsAre(LanguageModel::LanguageInfo{kLang1, 1}));
 }
 
+TEST(LanguageModelTest, ShouldClearHistoryIfAllTimes) {
+  TestingPrefServiceSimple prefs;
+  LanguageModel::RegisterProfilePrefs(prefs.registry());
+  LanguageModel model(&prefs);
+
+  for (int i = 0; i < 100; i++) {
+    model.OnPageVisited(kLang1);
+  }
+
+  EXPECT_THAT(model.GetTopLanguages(), SizeIs(1));
+  EXPECT_THAT(model.GetLanguageFrequency(kLang1), FloatEq(1.0));
+
+  model.ClearHistory(base::Time(), base::Time::Max());
+
+  EXPECT_THAT(model.GetTopLanguages(), SizeIs(0));
+  EXPECT_THAT(model.GetLanguageFrequency(kLang1), FloatEq(0.0));
+}
+
+TEST(LanguageModelTest, ShouldNotClearHistoryIfNotAllTimes) {
+  TestingPrefServiceSimple prefs;
+  LanguageModel::RegisterProfilePrefs(prefs.registry());
+  LanguageModel model(&prefs);
+
+  for (int i = 0; i < 100; i++) {
+    model.OnPageVisited(kLang1);
+  }
+
+  EXPECT_THAT(model.GetTopLanguages(), SizeIs(1));
+  EXPECT_THAT(model.GetLanguageFrequency(kLang1), FloatEq(1.0));
+
+  // Clearing only the last hour of the history has no effect.
+  model.ClearHistory(base::Time::Now() - base::TimeDelta::FromHours(2),
+                     base::Time::Max());
+
+  EXPECT_THAT(model.GetTopLanguages(), SizeIs(1));
+  EXPECT_THAT(model.GetLanguageFrequency(kLang1), FloatEq(1.0));
+}
+
 }  // namespace translate