Implementing answer card hover highlight.

ui/app_list/search_result_observer.h

Index: ui/app_list/search_result_observer.h
diff --git a/ui/app_list/search_result_observer.h b/ui/app_list/search_result_observer.h
index 72ed4fb25d56c0fc4276b713e8cd9d32f0a539ff..53220028307dd20c2b862fdbcbf180c31da725a4 100644
--- a/ui/app_list/search_result_observer.h
+++ b/ui/app_list/search_result_observer.h
@@ -32,6 +32,10 @@ class APP_LIST_EXPORT SearchResultObserver {
   // Invoked just before the SearchResult is destroyed.
   virtual void OnResultDestroying() {}
 
+  // Invoked when SearchResult has an associated view, and the mouse cursor
+  // enters or exits that view.

[xiyuan, 2017/06/06 18:53:53]

nit: Document that it is needed because the view is views::WebView and existing
views mouse enter/exit events does not fire on it.

[vadimt, 2017/06/06 19:18:54]

Done.

+  virtual void OnViewHoverStateChanged() {}
+
  protected:
   virtual ~SearchResultObserver() {}
 };