Omnibox: Add Field Trial for Demoting/Disabling Search History

Adds a field trial that tries:
* demoting search history suggestions (so they never appear inline)
* disabling search history suggestions (so they never appear)

Note that query suggestions from the suggest server can still be
inlined, so if you test this with a popular query you may be misled into
thinking the trial isn't working because you're still see the
suggestion. Check about:omnibox to see where the suggestion is coming
from.

Tested using --force-fieldtrials and about:omnibox
BUG=172491

Review URL: https://chromiumcodereview.appspot.com/18870004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@210802 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 47 insertions, 6 deletions

diff --git a/chrome/browser/autocomplete/search_provider.cc b/chrome/browser/autocomplete/search_provider.cc
index c5861c4..2f30450 100644
--- a/chrome/browser/autocomplete/search_provider.cc
+++ b/chrome/browser/autocomplete/search_provider.cc
@@ -251,7 +251,11 @@ SearchProvider::SearchProvider(AutocompleteProviderListener* listener,
       suggest_results_pending_(0),
       field_trial_triggered_(false),
       field_trial_triggered_in_session_(false),
-      omnibox_start_margin_(-1) {
+      omnibox_start_margin_(-1),
+      prevent_search_history_inlining_(
+          OmniboxFieldTrial::SearchHistoryPreventInlining()),
+      disable_search_history_(
+          OmniboxFieldTrial::SearchHistoryDisable()) {
 }
 
 // static
@@ -627,6 +631,9 @@ void SearchProvider::DoHistoryQuery(bool minimal_changes) {
   keyword_history_results_.clear();
   default_history_results_.clear();
 
+  if (disable_search_history_)
+    return;
+
   HistoryService* const history_service =
       HistoryServiceFactory::GetForProfile(profile_, Profile::EXPLICIT_ACCESS);
   history::URLDatabase* url_db = history_service ?
@@ -1336,17 +1343,21 @@ int SearchProvider::CalculateRelevanceForHistory(
     bool prevent_inline_autocomplete) const {
   // The relevance of past searches falls off over time. There are two distinct
   // equations used. If the first equation is used (searches to the primary
-  // provider that we want to inline autocomplete), the score starts at 1399 and
-  // falls to 1300. If the second equation is used the relevance of a search 15
-  // minutes ago is discounted 50 points, while the relevance of a search two
-  // weeks ago is discounted 450 points.
+  // provider that we want to inline autocomplete), the score is in the range
+  // 1300-1599 (unless |prevent_search_history_inlining_|, in which case
+  // it's in the range 1200-1299). If the second equation is used the
+  // relevance of a search 15 minutes ago is discounted 50 points, while the
+  // relevance of a search two weeks ago is discounted 450 points.
   double elapsed_time = std::max((base::Time::Now() - time).InSecondsF(), 0.0);
   bool is_primary_provider = is_keyword || !providers_.has_keyword_provider();
   if (is_primary_provider && !prevent_inline_autocomplete) {
     // Searches with the past two days get a different curve.
     const double autocomplete_time = 2 * 24 * 60 * 60;
     if (elapsed_time < autocomplete_time) {
-      return (is_keyword ? 1599 : 1399) - static_cast<int>(99 *
+      int max_score = is_keyword ? 1599 : 1399;
+      if (prevent_search_history_inlining_)
+        max_score = 1299;
+      return max_score - static_cast<int>(99 *
           std::pow(elapsed_time / autocomplete_time, 2.5));
     }
     elapsed_time -= autocomplete_time;
diff --git a/chrome/browser/autocomplete/search_provider.h b/chrome/browser/autocomplete/search_provider.h
index 59ecc79..f01fdb6 100644
--- a/chrome/browser/autocomplete/search_provider.h
+++ b/chrome/browser/autocomplete/search_provider.h
@@ -527,6 +527,13 @@ class SearchProvider : public AutocompleteProvider,
   // Start margin of the omnibox. Used to construct search URLs.
   int omnibox_start_margin_;
 
+  // If true, search history query suggestions will score low enough that
+  // they will not be inlined.
+  bool prevent_search_history_inlining_;
+
+  // If true, no search history query suggestions will be offered.
+  bool disable_search_history_;
+
   DISALLOW_COPY_AND_ASSIGN(SearchProvider);
 };
 
diff --git a/chrome/browser/omnibox/omnibox_field_trial.cc b/chrome/browser/omnibox/omnibox_field_trial.cc
index da16943..514c669 100644
--- a/chrome/browser/omnibox/omnibox_field_trial.cc
+++ b/chrome/browser/omnibox/omnibox_field_trial.cc
@@ -23,6 +23,7 @@ const char kHUPCreateShorterMatchFieldTrialName[] =
     "OmniboxHUPCreateShorterMatch";
 const char kStopTimerFieldTrialName[] = "OmniboxStopTimer";
 const char kShortcutsScoringFieldTrialName[] = "OmniboxShortcutsScoring";
+const char kSearchHistoryFieldTrialName[] = "OmniboxSearchHistory";
 
 // The autocomplete dynamic field trial name prefix.  Each field trial is
 // configured dynamically and is retrieved automatically by Chrome during
@@ -258,3 +259,13 @@ bool OmniboxFieldTrial::ShortcutsScoringMaxRelevance(int* max_relevance) {
   }
   return true;
 }
+
+bool OmniboxFieldTrial::SearchHistoryPreventInlining() {
+  return (base::FieldTrialList::FindFullName(kSearchHistoryFieldTrialName) ==
+          "PreventInlining");
+}
+
+bool OmniboxFieldTrial::SearchHistoryDisable() {
+  return (base::FieldTrialList::FindFullName(kSearchHistoryFieldTrialName) ==
+          "Disable");
+}
diff --git a/chrome/browser/omnibox/omnibox_field_trial.h b/chrome/browser/omnibox/omnibox_field_trial.h
index ab5babc..5a928be 100644
--- a/chrome/browser/omnibox/omnibox_field_trial.h
+++ b/chrome/browser/omnibox/omnibox_field_trial.h
@@ -113,6 +113,18 @@ class OmniboxFieldTrial {
   // inlined.)
   static bool ShortcutsScoringMaxRelevance(int* max_relevance);
 
+  // ---------------------------------------------------------
+  // For the SearchHistory field trial.
+
+  // Returns true if the user is in the experiment group that scores
+  // search history query suggestions less aggressively so that they don't
+  // inline.
+  static bool SearchHistoryPreventInlining();
+
+  // Returns true if the user is in the experiment group that disables
+  // all query suggestions from search history.
+  static bool SearchHistoryDisable();
+
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(OmniboxFieldTrial);
 };