Don't demote top match for certain match types.

chrome/browser/omnibox/omnibox_field_trial.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/omnibox/omnibox_field_trial.h"
 
 #include <string>
 
 #include "base/metrics/field_trial.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 247 matching lines @@
       // errors smartly.
       int k, v;
       base::StringToInt(it->first, &k);
       base::StringToInt(it->second, &v);
       (*demotions_by_type)[static_cast<AutocompleteMatchType::Type>(k)] =
           static_cast<float>(v) / 100.0f;
     }
   }
 }
 
+void OmniboxFieldTrial::GetUndemotableTopTypes(

[Peter Kasting, 2013/11/05 04:09:55]

This should return by value rather than outparam.  I assume you're trying to use
outparams for efficiency reasons, but in this case the RVO should eliminate any
performance difference, and this function reads better and would have simpler
callsites with return-by-value.

[H Fung, 2013/11/05 06:11:27]

Done.

+    AutocompleteInput::PageClassification current_page_classification,
+    UndemotableTopMatchTypes* undemotable_types) {
+  undemotable_types->clear();
+  const std::string types_rule =
+      OmniboxFieldTrial::GetValueForRuleInContext(
+          kUndemotableTopTypeRule,
+          current_page_classification);
+  // The value of the UndemotableTopTypes rule is a comma-separated list of
+  // AutocompleteMatchType::Type enums represented as an integer. The
+  // DemoteByType rule does not apply to the top match if the type of the top
+  // match is in this list.
+  std::vector<std::string> types;
+  base::SplitString(types_rule, ',', &types);
+  for (std::vector<std::string>::const_iterator it = types.begin();
+       it != types.end(); ++it) {
+    // This is a best-effort conversion; we trust the hand-crafted parameters
+    // downloaded from the server to be perfect.  There's no need for handle

[Peter Kasting, 2013/11/05 04:09:55]

Nit: for -> to (and fix above code also)

[H Fung, 2013/11/05 06:11:27]

Done.

+    // errors smartly.
+    int t;
+    base::StringToInt(*it, &t);
+    undemotable_types->insert(static_cast<AutocompleteMatchType::Type>(t));
+  }
+}
+
 bool OmniboxFieldTrial::ReorderForLegalDefaultMatch(
     AutocompleteInput::PageClassification current_page_classification) {
   return OmniboxFieldTrial::GetValueForRuleInContext(
       kReorderForLegalDefaultMatchRule, current_page_classification) ==
       kReorderForLegalDefaultMatchRuleEnabled;
 }
 
 const char OmniboxFieldTrial::kBundledExperimentFieldTrialName[] =
     "OmniboxBundledExperimentV1";
 const char OmniboxFieldTrial::kShortcutsScoringMaxRelevanceRule[] =
     "ShortcutsScoringMaxRelevance";
 const char OmniboxFieldTrial::kSearchHistoryRule[] = "SearchHistory";
 const char OmniboxFieldTrial::kDemoteByTypeRule[] = "DemoteByType";
+const char OmniboxFieldTrial::kUndemotableTopTypeRule[] = "UndemotableTopTypes";
 const char OmniboxFieldTrial::kReorderForLegalDefaultMatchRule[] =
     "ReorderForLegalDefaultMatch";
 const char OmniboxFieldTrial::kReorderForLegalDefaultMatchRuleEnabled[] =
     "ReorderForLegalDefaultMatch";
 
 // Background and implementation details:
 //
 // Each experiment group in any field trial can come with an optional set of
 // parameters (key-value pairs).  In the bundled omnibox experiment
 // (kBundledExperimentFieldTrialName), each experiment group comes with a
@@ skipping 47 matching lines @@
   if (it != params.end())
     return it->second;
   // Fall back to the global instant extended context.
   it = params.find(rule + ":" + page_classification_str + ":*");
   if (it != params.end())
     return it->second;
   // Look up rule in the global context.
   it = params.find(rule + ":*:*");
   return (it != params.end()) ? it->second : std::string();
 }