Refactor AddScrollListItem() in system menu detailed views

ash/system/tray/hover_highlight_view.h

Index: ash/system/tray/hover_highlight_view.h
diff --git a/ash/system/tray/hover_highlight_view.h b/ash/system/tray/hover_highlight_view.h
index 300a6e3c793c87a6fb2f0b931ce280511d69432c..6e3c81110f1249588d6ed0f5e1e0f47b7407a299 100644
--- a/ash/system/tray/hover_highlight_view.h
+++ b/ash/system/tray/hover_highlight_view.h
@@ -68,6 +68,11 @@ class HoverHighlightView : public ActionableView {
   // Hide or show the right view.
   void SetRightViewVisible(bool visible);
 
+  // Sets text for the sub label. Precondition for this function is that the
+  // main label should be present. Empty string can be used to clear the sub

[tdanderson, 2017/04/24 15:43:39]

nit: instead say something like "|text_label_| is non-null / nonempty" (call out
the variable by name) instead of "the main label should be present"

[mohsen, 2017/04/25 05:10:01]

Done.

+  // label.
+  void SetSubText(const base::string16& sub_text);
+
   // Allows view to expand its height. Size of unexapandable view is fixed and
   // equals to kTrayPopupItemHeight.
   void SetExpandable(bool expandable);