Simplify TranslateRanker API.

components/translate/core/browser/translate_ranker_impl.cc

Index: components/translate/core/browser/translate_ranker_impl.cc
diff --git a/components/translate/core/browser/translate_ranker_impl.cc b/components/translate/core/browser/translate_ranker_impl.cc
index c9aed1ec829cb7a5dc1030e4c3f690207f7ce396..9d97a766604eada0b8840ba01be5035fe39b2cc4 100644
--- a/components/translate/core/browser/translate_ranker_impl.cc
+++ b/components/translate/core/browser/translate_ranker_impl.cc
@@ -15,7 +15,6 @@
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/metrics_hashes.h"
 #include "base/profiler/scoped_tracker.h"
-#include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ -23,9 +22,6 @@
 #include "components/translate/core/browser/proto/ranker_model.pb.h"
 #include "components/translate/core/browser/proto/translate_ranker_model.pb.h"
 #include "components/translate/core/browser/ranker_model.h"
-#include "components/translate/core/browser/translate_download_manager.h"
-#include "components/translate/core/browser/translate_prefs.h"
-#include "components/translate/core/browser/translate_url_fetcher.h"
 #include "components/translate/core/common/translate_switches.h"
 #include "components/ukm/ukm_entry_builder.h"
 #include "components/ukm/ukm_service.h"
@@ -106,17 +102,16 @@ TranslateRankerFeatures::TranslateRankerFeatures(int accepted,
       denied_ratio(SafeRatio(denied_count, total_count)),
       ignored_ratio(SafeRatio(ignored_count, total_count)) {}
 
-TranslateRankerFeatures::TranslateRankerFeatures(const TranslatePrefs& prefs,
-                                                 const std::string& src,
-                                                 const std::string& dst,
-                                                 const std::string& locale)
-    : TranslateRankerFeatures(prefs.GetTranslationAcceptedCount(src),
-                              prefs.GetTranslationDeniedCount(src),
-                              prefs.GetTranslationIgnoredCount(src),
-                              src,
-                              dst,
-                              prefs.GetCountry(),
-                              locale) {}
+// TODO(hamelphi): Log locale in TranslateEventProtos.
+TranslateRankerFeatures::TranslateRankerFeatures(
+    const metrics::TranslateEventProto& translate_event)
+    : TranslateRankerFeatures(translate_event.accept_count(),
+                              translate_event.decline_count(),
+                              translate_event.ignore_count(),
+                              translate_event.source_language(),
+                              translate_event.target_language(),
+                              translate_event.country(),
+                              "" /*locale*/) {}
 
 TranslateRankerFeatures::~TranslateRankerFeatures() {}
 
@@ -195,9 +190,6 @@ uint32_t TranslateRankerImpl::GetModelVersion() const {
 }
 
 bool TranslateRankerImpl::ShouldOfferTranslation(
-    const TranslatePrefs& translate_prefs,
-    const std::string& src_lang,
-    const std::string& dst_lang,
     metrics::TranslateEventProto* translate_event) {
   DCHECK(sequence_checker_.CalledOnValidSequence());
   // The ranker is a gate in the "show a translation prompt" flow. To retain
@@ -234,11 +226,8 @@ bool TranslateRankerImpl::ShouldOfferTranslation(
       FROM_HERE_WITH_EXPLICIT_FUNCTION(
           "646711 translate::TranslateRankerImpl::ShouldOfferTranslation"));
 
-  TranslateRankerFeatures features(
-      translate_prefs, src_lang, dst_lang,
-      TranslateDownloadManager::GetInstance()->application_locale());
+  bool result = GetModelDecision(*translate_event);
 
-  bool result = GetModelDecision(features);
   UMA_HISTOGRAM_BOOLEAN("Translate.Ranker.QueryResult", result);
 
   translate_event->set_ranker_response(
@@ -253,33 +242,38 @@ bool TranslateRankerImpl::ShouldOfferTranslation(
 }
 
 bool TranslateRankerImpl::GetModelDecision(
-    const TranslateRankerFeatures& features) {
+    const metrics::TranslateEventProto& translate_event) {
   DCHECK(sequence_checker_.CalledOnValidSequence());
   SCOPED_UMA_HISTOGRAM_TIMER("Translate.Ranker.Timer.CalculateScore");
   DCHECK(model_ != nullptr);
-  const TranslateRankerModel::LogisticRegressionModel& logit =
+
+  // TODO(hamelphi): consider deprecating TranslateRankerFeatures and move the
+  // logic here.
+  const TranslateRankerFeatures features(translate_event);
+
+  const TranslateRankerModel::LogisticRegressionModel& lr_model =
       model_->proto().translate().logistic_regression_model();
 
   double dot_product =
-      (features.accepted_count * logit.accept_count_weight()) +
-      (features.denied_count * logit.decline_count_weight()) +
-      (features.ignored_count * logit.ignore_count_weight()) +
-      (features.accepted_ratio * logit.accept_ratio_weight()) +
-      (features.denied_ratio * logit.decline_ratio_weight()) +
-      (features.ignored_ratio * logit.ignore_ratio_weight()) +
-      ScoreComponent(logit.source_language_weight(), features.src_lang) +
-      ScoreComponent(logit.target_language_weight(), features.dst_lang) +
-      ScoreComponent(logit.country_weight(), features.country) +
-      ScoreComponent(logit.locale_weight(), features.app_locale);
-
-  double score = Sigmoid(dot_product + logit.bias());
+      (features.accepted_count * lr_model.accept_count_weight()) +
+      (features.denied_count * lr_model.decline_count_weight()) +
+      (features.ignored_count * lr_model.ignore_count_weight()) +
+      (features.accepted_ratio * lr_model.accept_ratio_weight()) +
+      (features.denied_ratio * lr_model.decline_ratio_weight()) +
+      (features.ignored_ratio * lr_model.ignore_ratio_weight()) +
+      ScoreComponent(lr_model.source_language_weight(), features.src_lang) +
+      ScoreComponent(lr_model.target_language_weight(), features.dst_lang) +
+      ScoreComponent(lr_model.country_weight(), features.country) +
+      ScoreComponent(lr_model.locale_weight(), features.app_locale);
+
+  double score = Sigmoid(dot_product + lr_model.bias());
 
   DVLOG(2) << "TranslateRankerImpl::GetModelDecision: "
            << "Score = " << score << ", Features=[" << features << "]";
 
   float decision_threshold = kTranslationOfferDefaultThreshold;
-  if (logit.threshold() > 0) {
-    decision_threshold = logit.threshold();
+  if (lr_model.threshold() > 0) {
+    decision_threshold = lr_model.threshold();
   }
 
   return score >= decision_threshold;