Add Apps.AppListSearchResultDistanceFromOrigin UMA stat.

ui/app_list/search_result.h

Index: ui/app_list/search_result.h
diff --git a/ui/app_list/search_result.h b/ui/app_list/search_result.h
index e571316587c0312ba225a20452a4a8edef72f4dc..314746f9744cecec2de61ec426fece93c78350c3 100644
--- a/ui/app_list/search_result.h
+++ b/ui/app_list/search_result.h
@@ -111,6 +111,11 @@ class APP_LIST_EXPORT SearchResult {
     display_type_ = display_type;
   }
 
+  int distance_from_origin() { return distance_from_origin_; }
+  void set_distance_from_origin(int distance) {
+    distance_from_origin_ = distance;
+  }
+
   const Actions& actions() const {
     return actions_;
   }
@@ -169,6 +174,10 @@ class APP_LIST_EXPORT SearchResult {
   double relevance_;
   DisplayType display_type_;
 
+  // The Manhattan distance from the origin of all search results to this
+  // result. This is logged for UMA.
+  int distance_from_origin_;
+
   Actions actions_;
   bool voice_result_;