Add Apps.AppListSearchResultDistanceFromOrigin UMA stat.

ui/app_list/views/search_result_container_view.h

Index: ui/app_list/views/search_result_container_view.h
diff --git a/ui/app_list/views/search_result_container_view.h b/ui/app_list/views/search_result_container_view.h
index c2fafe326966ced80ca319021c10b3bb70c49b69..a0644ee64f6be6cf83fbec731bdeca0ce9b174c8 100644
--- a/ui/app_list/views/search_result_container_view.h
+++ b/ui/app_list/views/search_result_container_view.h
@@ -43,10 +43,21 @@ class APP_LIST_EXPORT SearchResultContainerView : public views::View,
   void set_container_score(double score) { container_score_ = score; }
   double container_score() const { return container_score_; }
 
+  // Notifies the container of the y-index of the first result of this container
+  // relative to all other result containers.
+  virtual void NotifyFirstResultYIndex(int y_index) = 0;

[Matt Giuca, 2015/05/11 06:50:40]

The documentation should say what this function *does*, not what its caller
does.

Also "relative to all other result containers" doesn't make sense; it is
absolute, not relative to any particular container.

How about:
// Updates the distance_from_origin() properties of the results in this
container. |y_index| is the absolute y-index of the first result of this
container (counting from the top of the app list).

[calamity, 2015/05/11 07:15:03]

Done.

+
+  // Gets the number of down keystrokes from the beginning to the end of this
+  // container.
+  virtual int GetYSize() = 0;
+
   // Schedules an Update call using |update_factory_|. Do nothing if there is a
   // pending call.
   void ScheduleUpdate();
 
+  // Returns whether an update is currently scheduled for this container.
+  bool UpdateScheduled();
+
   // Overridden from ui::ListModelObserver:
   void ListItemsAdded(size_t start, size_t count) override;
   void ListItemsRemoved(size_t start, size_t count) override;