Optimize shortcuts provider

components/omnibox/browser/match_compare.h

+// 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.
+
+#ifndef COMPONENTS_OMNIBOX_BROWSER_MATCH_COMPARE_H_
+#define COMPONENTS_OMNIBOX_BROWSER_MATCH_COMPARE_H_
+
+#include "components/omnibox/browser/omnibox_field_trial.h"
+
+// This class implements a special version of AutocompleteMatch::MoreRelevant
+// that allows matches of particular types to be demoted in AutocompleteResult.
+template <class Match>
+class CompareWithDemoteByType {
+ public:
+  CompareWithDemoteByType(
+      metrics::OmniboxEventProto::PageClassification page_classification) {
+    OmniboxFieldTrial::GetDemotionsByType(page_classification, &demotions_);
+  }
+
+  // Returns the relevance score of |match| demoted appropriately by
+  // |demotions_by_type_|.
+  int GetDemotedRelevance(const Match& match) const {
+    OmniboxFieldTrial::DemotionMultipliers::const_iterator demotion_it =
+        demotions_.find(match.type);
+    return (demotion_it == demotions_.end())
+               ? match.relevance
+               : (match.relevance * demotion_it->second);
+  }
+
+  // Comparison function.
+  bool operator()(const Match& elem1, const Match& elem2) {
+    // Compute demoted relevance scores for each match.
+    const int demoted_relevance1 = GetDemotedRelevance(elem1);
+    const int demoted_relevance2 = GetDemotedRelevance(elem2);
+    // For equal-relevance matches, we sort alphabetically, so that providers
+    // who return multiple elements at the same priority get a "stable" sort
+    // across multiple updates.
+    return (demoted_relevance1 == demoted_relevance2)
+               ? (elem1.contents < elem2.contents)
+               : (demoted_relevance1 > demoted_relevance2);
+  }
+
+ private:
+  OmniboxFieldTrial::DemotionMultipliers demotions_;
+};
+
+template <class Match>
+class DestinationSort {
+ public:
+  DestinationSort(
+      metrics::OmniboxEventProto::PageClassification page_classification)
+      : demote_by_type_(page_classification) {}
+  bool operator()(const Match& elem1, const Match& elem2) {
+    // Sort identical destination_urls together.
+    // Place the most relevant matches first, so that when we call
+    // std::unique(), these are the ones that get preserved.
+    return (elem1.stripped_destination_url == elem2.stripped_destination_url)
+               ? demote_by_type_(elem1, elem2)
+               : (elem1.stripped_destination_url <
+                  elem2.stripped_destination_url);
+  }
+
+ private:
+  CompareWithDemoteByType<Match> demote_by_type_;
+};
+
+#endif  // COMPONENTS_OMNIBOX_BROWSER_MATCH_COMPARE_H_