Add LanguageModel, a keyed service that collects language info from CLD.

components/translate/core/browser/language_model_unittest.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 "components/prefs/testing_pref_service.h"
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using testing::ElementsAre;
+using testing::FloatEq;
+using testing::Ge;
+
+namespace {
+
+const char kLang1[] = "en";
+const char kLang2[] = "de";
+const char kLang3[] = "es";
+
+}  // namespace
+
+namespace translate {
+
+TEST(LanguageModelTest, ListSorted) {
+  TestingPrefServiceSimple prefs;
+  LanguageModel::RegisterProfilePrefs(prefs.registry());
+  LanguageModel model(&prefs);
+
+  model.OnPageVisited(kLang1);
+  model.OnPageVisited(kLang1);
+  model.OnPageVisited(kLang1);
+  model.OnPageVisited(kLang2);
+
+  EXPECT_THAT(model.GetTopLanguages(),
+              ElementsAre(LanguageModel::LanguageInfo{kLang1},
+                          LanguageModel::LanguageInfo{kLang2}));
+}
+
+TEST(LanguageModelTest, ListSortedReversed) {
+  TestingPrefServiceSimple prefs;
+  LanguageModel::RegisterProfilePrefs(prefs.registry());
+  LanguageModel model(&prefs);
+
+  model.OnPageVisited(kLang2);
+  model.OnPageVisited(kLang1);
+  model.OnPageVisited(kLang1);
+  model.OnPageVisited(kLang1);
+
+  EXPECT_THAT(model.GetTopLanguages(),
+              ElementsAre(LanguageModel::LanguageInfo{kLang1},
+                          LanguageModel::LanguageInfo{kLang2}));
+}
+
+TEST(LanguageModelTest, RightFrequencies) {
+  TestingPrefServiceSimple prefs;
+  LanguageModel::RegisterProfilePrefs(prefs.registry());
+  LanguageModel model(&prefs);
+
+  model.OnPageVisited(kLang1);
+  model.OnPageVisited(kLang1);
+  model.OnPageVisited(kLang1);
+  model.OnPageVisited(kLang2);
+
+  // Corresponding frequencies are given by the model.
+  EXPECT_THAT(model.GetLanguageFrequency(kLang1), FloatEq(0.75f));
+  EXPECT_THAT(model.GetLanguageFrequency(kLang2), FloatEq(0.25f));
+  // An unknown language gets frequency 0.
+  EXPECT_THAT(model.GetLanguageFrequency(kLang3), 0);
+}
+
+TEST(LanguageModelTest, RareLanguageDiscarded) {
+  TestingPrefServiceSimple prefs;
+  LanguageModel::RegisterProfilePrefs(prefs.registry());
+  LanguageModel model(&prefs);
+
+  model.OnPageVisited(kLang2);
+
+  for (int i = 0; i < 900; i++)
+    model.OnPageVisited(kLang1);
+
+  // Lang 2 is in the model.
+  EXPECT_THAT(model.GetLanguageFrequency(kLang2), Ge(0.0f));

[Bernhard Bauer, 2016/10/06 08:58:49]

Do you want Gt() here? GetLanguageFrequency returns 0 for an unknown language,
right?

[jkrcal, 2016/10/06 09:38:37]

Oh, true. Thanks for spotting it!

+
+  // Another 100 visits cause the cleanup (total > 1000).
+  for (int i = 0; i < 100; i++)
+    model.OnPageVisited(kLang1);
+  // Lang 2 is removed from the model.
+  EXPECT_THAT(model.GetTopLanguages(),
+              ElementsAre(LanguageModel::LanguageInfo{kLang1, 1}));
+}
+
+}  // namespace translate