Omnibox: Convert Shortcuts Scoring Field Trial to Omnibox Bundled Field Trial

chrome/browser/autocomplete/shortcuts_provider.cc

 // Copyright (c) 2012 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 "chrome/browser/autocomplete/shortcuts_provider.h"
 
 #include <algorithm>
 #include <cmath>
 #include <map>
 #include <vector>
@@ skipping 36 matching lines @@
   const std::set<GURL>& urls_;
 };
 
 }  // namespace
 
 ShortcutsProvider::ShortcutsProvider(AutocompleteProviderListener* listener,
                                      Profile* profile)
     : AutocompleteProvider(listener, profile,
           AutocompleteProvider::TYPE_SHORTCUTS),
       languages_(profile_->GetPrefs()->GetString(prefs::kAcceptLanguages)),
-      initialized_(false),
-      max_relevance_(AutocompleteResult::kLowestDefaultScore - 1) {
+      initialized_(false) {
   scoped_refptr<history::ShortcutsBackend> backend =
       ShortcutsBackendFactory::GetForProfile(profile_);
   if (backend.get()) {
     backend->AddObserver(this);
     if (backend->initialized())
       initialized_ = true;
   }
-  int max_relevance;
-  if (OmniboxFieldTrial::ShortcutsScoringMaxRelevance(&max_relevance))
-    max_relevance_ = max_relevance;
 }
 
 void ShortcutsProvider::Start(const AutocompleteInput& input,
                               bool minimal_changes) {
   matches_.clear();
 
   if ((input.type() == AutocompleteInput::INVALID) ||
       (input.type() == AutocompleteInput::FORCED_QUERY))
     return;
 
@@ skipping 71 matching lines @@
 void ShortcutsProvider::GetMatches(const AutocompleteInput& input) {
   scoped_refptr<history::ShortcutsBackend> backend =
       ShortcutsBackendFactory::GetForProfileIfExists(profile_);
   if (!backend.get())
     return;
   // Get the URLs from the shortcuts database with keys that partially or
   // completely match the search term.
   string16 term_string(base::i18n::ToLower(input.text()));
   DCHECK(!term_string.empty());
 
+  int max_relevance;
+  if (!OmniboxFieldTrial::ShortcutsScoringMaxRelevance(

[Peter Kasting, 2013/08/09 23:33:15]

Nit: Perhaps we should default-initialize the temp, and simply make this
function not touch its argument on failure.  Then we need not even have a return
value.

[Mark P, 2013/08/10 00:11:56]

I prefer this type of structure (success_bool, variable_to_set).  I've run into
too many annoying interfaces that make it difficult to tell the difference
between failure and success but empty or success but no need to modify.

+      input.current_page_classification(), &max_relevance))
+    max_relevance = AutocompleteResult::kLowestDefaultScore - 1;
+
   for (history::ShortcutsBackend::ShortcutMap::const_iterator it =
            FindFirstMatch(term_string, backend.get());
        it != backend->shortcuts_map().end() &&
            StartsWith(it->first, term_string, true); ++it) {
     // Don't return shortcuts with zero relevance.
-    int relevance = CalculateScore(term_string, it->second);
+    int relevance = CalculateScore(term_string, it->second, max_relevance);
     if (relevance)
       matches_.push_back(ShortcutToACMatch(relevance, term_string, it->second));
   }
   std::partial_sort(matches_.begin(),
       matches_.begin() +
           std::min(AutocompleteProvider::kMaxMatches, matches_.size()),
       matches_.end(), &AutocompleteMatch::MoreRelevant);
   if (matches_.size() > AutocompleteProvider::kMaxMatches) {
     matches_.erase(matches_.begin() + AutocompleteProvider::kMaxMatches,
                    matches_.end());
   }
   // Reset relevance scores to guarantee no results are given an
   // inlineable score and all scores are decreasing (but not do assign
   // any scores below 1).
-  int max_relevance = AutocompleteResult::kLowestDefaultScore - 1;
+  max_relevance = AutocompleteResult::kLowestDefaultScore - 1;
   for (ACMatches::iterator it = matches_.begin(); it != matches_.end(); ++it) {
     max_relevance = std::min(max_relevance, it->relevance);
     it->relevance = max_relevance;
     if (max_relevance > 1)
       --max_relevance;
   }
 }
 
 AutocompleteMatch ShortcutsProvider::ShortcutToACMatch(
     int relevance,
@@ skipping 140 matching lines @@
       backend->shortcuts_map().lower_bound(keyword);
   // Lower bound not necessarily matches the keyword, check for item pointed by
   // the lower bound iterator to at least start with keyword.
   return ((it == backend->shortcuts_map().end()) ||
     StartsWith(it->first, keyword, true)) ? it :
     backend->shortcuts_map().end();
 }
 
 int ShortcutsProvider::CalculateScore(
     const string16& terms,
-    const history::ShortcutsBackend::Shortcut& shortcut) {
+    const history::ShortcutsBackend::Shortcut& shortcut,
+    int max_relevance) {
   DCHECK(!terms.empty());
   DCHECK_LE(terms.length(), shortcut.text.length());
 
   // The initial score is based on how much of the shortcut the user has typed.
   // Using the square root of the typed fraction boosts the base score rapidly
   // as characters are typed, compared with simply using the typed fraction
   // directly. This makes sense since the first characters typed are much more
   // important for determining how likely it is a user wants a particular
   // shortcut than are the remaining continued characters.
-  double base_score = max_relevance_ *
+  double base_score = max_relevance *
       sqrt(static_cast<double>(terms.length()) / shortcut.text.length());
 
   // Then we decay this by half each week.
   const double kLn2 = 0.6931471805599453;
   base::TimeDelta time_passed = base::Time::Now() - shortcut.last_access_time;
   // Clamp to 0 in case time jumps backwards (e.g. due to DST).
   double decay_exponent = std::max(0.0, kLn2 * static_cast<double>(
       time_passed.InMicroseconds()) / base::Time::kMicrosecondsPerWeek);
 
   // We modulate the decay factor based on how many times the shortcut has been
   // used. Newly created shortcuts decay at full speed; otherwise, decaying by
   // half takes |n| times as much time, where n increases by
   // (1.0 / each 5 additional hits), up to a maximum of 5x as long.
   const double kMaxDecaySpeedDivisor = 5.0;
   const double kNumUsesPerDecaySpeedDivisorIncrement = 5.0;
   double decay_divisor = std::min(kMaxDecaySpeedDivisor,
       (shortcut.number_of_hits + kNumUsesPerDecaySpeedDivisorIncrement - 1) /
       kNumUsesPerDecaySpeedDivisorIncrement);
 
   return static_cast<int>((base_score / exp(decay_exponent / decay_divisor)) +
       0.5);
 }