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..1ec8e3e265c8bdc8f5e462ffeb5e8fe6908b0097 100644
--- a/chrome/browser/omnibox/omnibox_field_trial.cc
+++ b/chrome/browser/omnibox/omnibox_field_trial.cc
@@ -265,6 +265,29 @@ void OmniboxFieldTrial::GetDemotionsByType(
   }
 }
 
+void OmniboxFieldTrial::GetUndemotableTopTypes(
+    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.

[Mark P, 2013/11/04 20:30:12]

Perhaps add something about demotion scores (refer to GetDemotionsByType) don't
get applied to a top match if the top match is of a type on this list.

[H Fung, 2013/11/04 21:39:57]

Done.

+  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
+    // 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 +301,7 @@ 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[] =