views: add focus ring to TreeView

ui/views/controls/focus_ring.h

Index: ui/views/controls/focus_ring.h
diff --git a/ui/views/controls/focus_ring.h b/ui/views/controls/focus_ring.h
index c2e6cfdf76c9310c400552fd36253a6e51626150..53aa19d3b6262938ae598281fe969992c268a24a 100644
--- a/ui/views/controls/focus_ring.h
+++ b/ui/views/controls/focus_ring.h
@@ -21,7 +21,7 @@ class FocusRing : public View {
   // Create a FocusRing and adds it to |parent|, or updates the one that already
   // exists. |override_color_id| will be used in place of the default coloration
   // when provided.
-  static void Install(views::View* parent,
+  static View* Install(views::View* parent,
                       ui::NativeTheme::ColorId override_color_id =
                           ui::NativeTheme::kColorId_NumColors);