Add a new entry to omnibox_event.proto to log specific type of contextual suggestions

components/omnibox/browser/omnibox_field_trial.h

Index: components/omnibox/browser/omnibox_field_trial.h
diff --git a/components/omnibox/browser/omnibox_field_trial.h b/components/omnibox/browser/omnibox_field_trial.h
index 2409711b18e74acf5538f06890b3bae1e0e47138..23afd4a00c514b3cc30c35e8a0625e07812b4662 100644
--- a/components/omnibox/browser/omnibox_field_trial.h
+++ b/components/omnibox/browser/omnibox_field_trial.h
@@ -133,6 +133,39 @@ class OmniboxFieldTrial {
     EMPHASIZE_NEVER = 3
   };
 
+  struct ContextualZeroSuggest {
+    enum Type {
+      NOT_SET = 0,
+      COOCCURENCE_PAGE = 1,
+      HIVEMIND_URL = 2,
+      LOCAL_STORE_MAP = 3,
+      LOCAL_STORE_WEBPAGE = 4,
+      LOCAL_STORE_RESERVATION = 5,
+      MOVIE_REVIEW = 6,
+      MOVIE_SHOWTIME = 7,
+      ON_THE_NEWS = 8,
+      POPULAR_DOMAINS = 9,
+      SIMILAR_PAGES = 10,
+      TOP_ENTITY_INFO = 11,
+      OTHER = 12,
+      NUM_TYPES,
+    };
+
+    // Converts |type| to a string representation.
+    static std::string ToString(const Type& type);
+
+    // Converts |type| from a string representation to Type.
+    static Type FromString(const std::string& type);
+
+    // Records the given type to the
+    // ZeroSuggest.ContextualSuggestType.SuggestionProvided histogram.
+    static void RecordTypeAsProvided(const std::string& type);
+
+    // Records the given type to the
+    // ZeroSuggest.ContextualSuggestType.SuggestionUsed histogram.
+    static void RecordTypeAsUsed(const std::string& type);
+  };
+
   // ---------------------------------------------------------
   // For any experiment that's part of the bundled omnibox field trial.