Don't demote top match for certain match types.

chrome/browser/omnibox/omnibox_field_trial.cc

Index: chrome/browser/omnibox/omnibox_field_trial.cc
diff --git a/chrome/browser/omnibox/omnibox_field_trial.cc b/chrome/browser/omnibox/omnibox_field_trial.cc
index e2c7144101483c2a6f0528524ec7d2854d086458..7688ca0e119d872a801931fd60d51fe1f20dc114 100644
--- a/chrome/browser/omnibox/omnibox_field_trial.cc
+++ b/chrome/browser/omnibox/omnibox_field_trial.cc
@@ -265,6 +265,31 @@ void OmniboxFieldTrial::GetDemotionsByType(
   }
 }
 
+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(
@@ -278,6 +303,7 @@ 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[] =